BOOKS  BY  EDWIN  C.  ECKEL 


Building  Stones  and  Clays:  their  Origin,  Characters 

and  Valuation.  8vo,  xiv  +  262  pages,  37  figures. 
Cloth,  $3.00  net.  JOHN  WILEY  &  SONS,  New 
York,  1912. 

Cements,  Limes  and  Plasters;  their  Materials,  Manu- 
facture and  Properties.  8vo,  xxxiv+yis  pages, 
165  figures,  254  Tables.  Cloth,  $6.00,  net.  JOHN 
WILEY  &  SONS,  New  York,  1905. 

Cement  Materials  and  Industry  of  the  United  States. 

Bulletin  No.  243,  U.  S.  Geological  Survey.  Svo, 
395  pages.  Washington,  1905.  (Out  of  print.) 

The  Portland  Cement  Industry  from  a  Financial 
Standpoint.  Svo,  93  pages.  MOODY  PUBLISHING 
Co.,  New  York,  1908 

The  Portland  Cement  Materials  of  the  United  States. 
Bulletin  No.  .  .  . ,  U.  S.  Geological  Survey.  Svo. 
Washington.  (In  Press.) 


BUILDING  STONES  AND  CLAYS: 


THEIR  ORIGIN,  CHARACTERS 
AND  EXAMINATION 


BY 

EDWIN   C.   ECKEL,   C.E. 

4     | 

ASSOCIATE,    AMERICAN   SOCIETY   OF   CIVIL   ENGINEERS 

MEMBER,    SOCIETY    OP    CHEMICAL    INDUSTRY 

FELLOW,  GEOLOGICAL  SOCIETY  OF  AMERICA 


FIRST   EDITION 
FIRST   THOUSAND 


NEW  YORK 

JOHN  WILEY  &  SONS 

LONDON:  CHAPMAN  &  HALL,  LIMITED 

1912 


3 


COPYRIGHT,  1912, 

BY 

EDWIN  C.  ECKEL,  C.E. 


Stanhope  jpress 

F.    H.  GILSON   COMPANY 
BOSTON.  U.S.A. 


To 
PROFESSOR  T.   NELSON  DALE 

Whose  work  on  slates  and  granites  has  at  last  given 

American  economic  geology  adequate 

representation  in  that  field. 


Cm.  ifi 

257977 


PREFACE 

THE  present  volume  may  in  some  sense  be  considered  as  an 
outgrowth  of  the  author's  previous  work  on  cementing  materials, 
for  it  deals  with  natural  materials  which  are  closely  related,  either 
as  constituents  or  as  competitors,  to  the  manufactured  products 
therein  discussed. 

It  may  be  noted  that  little  space  has  been  devoted  to  a  de- 
scription of  the  local  distribution  of  building  stones  and  clays. 
The  inclusion  of  such  data,  relative  to  products  which  are  nat- 
urally so  common  and  so  widely  distributed,  tends  to  convert  a 
general  treatise  into  a  mere  directory  of  the  quarry  and  clay 
product  industries.  The  extensive  reference  lists  which  are  pre- 
sented, however,  will  serve  to  point  out  where  information  re- 
garding the  stone  or  clays  of  any  particular  state  may  be  found. 
Attention  should  also  be  directed  to  the  chapters  relative  to 
the  examination  and  valuation  of  clay  and  stone  properties.  So 
far  as  known  to  the  writer,  most  of  the  material  therein  pre- 
sented has  not  been  touched  upon  in  earlier  works  on  these 
subjects. 

EDWIN  C.  ECKEL. 
WASHINGTON,  D.  C. 
January  13,  1912. 


TABLE  OF  CONTENTS 


PAGE 

Preface v 

Table  of  contents vii 

List  of  illustrations xiv 

PART   I. —  BUILDING  STONES. 
CHAPTER  I.  — THE   ORIGIN  AND   STRUCTURE   OF  ROCKS. 

The  engineering  applications  of  geology 1 

Outline  of  earth  history 1 

Relative  age  of  rocks 3 

Geologic  chronology 3 

The  geologic/viewpoint 4 

Kinds  of  rocks 5 

Metamorphism  of  rocks 6 

Conventional  symbols  for  rock  classes 6 

Chemical  relationships  of  the  rock  classes 7 

Genetic  relationship  of  the  rock  classes 8 

The  structures  of  rocks 11 

Inclination  of  beds;  dip  and  strike 11 

Rock  folds 12 

Faults  in  strata 13 

Joints 14 

Suggestions  for  geologic  reading 16 

CHAPTER  II.  — IGNEOUS  ROCKS  IN   GENERAL. 

Origin  of  igneous  rocks 17 

Modes  of  occurrence 17 

Texture  of  igneous  rocks 20 

Structure  of  igneous  masses 22 

Chemical  composition 22 

Mineral  constituents 24 

Quartz 25 

The  feldspars 25 

The  micas 26 

Amphibole-pyroxene  group 27 

Olivine  or  peridot 28 

Secondary  products 28 

Classification  of  igneous  rocks 28 

Commercial  classification 30 

vii 


viii  TABLE   OF   CONTENTS 

CHAPTER  m.  —  GRANITES  AND  OTHER  ACID  IGNEOUS  ROCKS. 

PAGE 

Scope  of  the  term  granite 32 

Origin  and  mode  of  occurrence 33 

Origin  of  granites 33 

Modes  of  occurrence 33 

Mineral  constitution 33 

Chief  constituent  minerals 33 

Identification  of  constituents 34 

Relative  proportions  of  minerals 34 

Color  of  granites 35 

Structure  and  texture 37 

Coarseness  of  crystallization 37 

Laminated  or  gneissoid  structure 37 

Sheet  structure 39 

Rift  and  grain 39 

Value  of  microscopic  work 41 

Chemical  composition  of  granites 41 

Value  of  chemical  work 41 

Normal  composition  of  granite 42 

Analyses  of  granites 43 

Physical  properties  of  granites 55 

Density  and  weight 55 

Compressive  strength 55 

Transverse  strength 60 

Geological  distribution  of  granites 60 

Production  of  granite  in  United  States 61 

References  on  granites 68 

CHAPTER  IV.  —  TRAP  ROCK  AND  OTHER  BASIC  IGNEOUS  STONES. 

Scope  of  term  trap  rock 70 

Occurrence  of  trap  rocks 70 

Color 71 

Mineral  constitution 71 

Identification  of  constituents 72 

Chemical  composition 72 

Analyses  of  trap  rocks 73 

Physical  properties 76 

Uses  of  trap  rock 77 

Production  of  trap  rock  in  the  United  States 78 

References  on  trap  rock 80 

CHAPTER  V.  —  SERPENTINE  AND  SOAPSTONE. 

Relation  of  serpentine  to  soapstone 81 

Serpentine 81 

Serpentine,  ophicalcite  and  ophimagnesite 81 

Origin  of  serpentines 82 

Chemical  composition  of  serpentine 83 

Defects  of  serpentine 85 


TABLE  OF  CONTENTS  ix 

PAGE 

Physical  properties 85 

Distribution  of  serpentine 86 

References  on  serpentine 87 

Soapstone  and  allied  products 87 

Origin  and  composition  of  soapstone .  .  '.  . 87 

Distribution  and  production 88 

References  on  talc  and  soapstone 90 

CHAPTER  VI.  —  SEDIMENTARY  ROCKS  IN  GENERAL. 

The  basis  for  classification 91 

Classes  of  sedimentary  rocks 92 

Degree  of  consolidation 92 

Modes  of  origin  of  sediments 92 

Characteristic  sedimentary  structures 93 

Metamorphism  and  its  effects 93 

Normal  order  of  discussion  of  the  sedimentary  rocks 93 

CHAPTER  VII.  — SLATES. 

Origin  and  composition 95 

Origin  of  slates 95 

Average  composition  of  slates 96 

Average  composition  of  shales 97 

Comparison  of  slate  and  shale  composition 98 

Origin  and  composition  of  igneous  slates 99 

References  on  origin  and  composition  of  slates 101 

Analyses  of  American  and  foreign  slates 102 

Color,  texture  and  structures 108 

Color  of  slates 108 

Economic  importance  of  color 109 

Cleavage 110 

Physical  properties  and  testing Ill 

Desirable  properties  of  slate Ill 

Specific  gravity  of  slates 112 

Merriman's  tests  of  roofing  slates 112 

References  on  properties  and  tests  of  slate 112 

Distribution  and  production  of  slate 113 

Geologic  distribution  of  slates 113 

Geographic  distribution  of  slates 113 

Chief  American  quarry  districts 114 

Chief  foreign  districts 115 

Dressing  of  roofing  slates 115 

Measurement  of  roofing  slates 119 

Sizes  of  slates 120 

Thickness 121 

Statistics  of  production  in  United  States 122 

Imports  and  exports  of  slate 125 

References  on  slate  deposits 125 


X  TABLE  OF  CONTENTS 

CHAPTER  VIH.  —  SANDSTONES. 

PAGE 

Scope  of  term  sandstone 127 

Origin  and  composition 127 

Origin  of  sandstones 127 

Origin  of  tuffs 1 128 

Chemical  composition  of  sandstones 128 

Value  of  chemical  work 129 

Interpretation  of  the  chemical  analysis 129 

Analyses  of  American  sandstones 131 

Texture  and  physical  properties 137 

Shape  and  size  of  grain 137 

Composition  of  the  cementing  material 137 

Value  of  microscopic  work 137 

Physical  properties  of  sandstones 138 

Working  classification  of  sandstones 142 

Necessity  for  subdivision 142 

(a)  Quartzites  and  quartzitic  sandstones 142 

(b)  Gray wackes  and  dense  flagstones 143 

(c)  Normal  sandstones 143 

(d)  Porous  sandstones 143 

Geologic  distribution  of  sandstones 143 

Production  of  sandstone  in  United  States 144 

References  on  sandstones ., 148 

CHAPTER  IX.  —  LIMESTONES. 

Origin  and  chemical  composition 150 

Origin  of  limestones 150 

Shells  as  sources  of  limestone 151 

Chemical  composition  of  limestone 152 

Presence  of  magnesia 152 

Presence  of  impurities 153 

Average  composition  of  limestones 154 

Analyses  of  American  limestones 155 

Physical  characters  and  tests 156 

Texture  and  structure 156 

Color 156 

Varieties  of  limestone 157 

Physical  characters 157 

Compressive  strength 158 

Distribution  and  production 159 

Geologic  and  geographic  distribution 159 

References  on  limestone  distribution 160 

Production  of  limestone  in  the  United  States 162 

CHAPTER   X.  — MARBLES. 

Varieties  of  marble 166 

Highly  crystalline  marbles 166 

Origin  and  character 167 


TABLE  OF  CONTENTS  XI 

PAGE 

Chemical  composition -. 167 

Physical  properties 172 

Production 174 

References 175 

Fossilif erous  or  sub-crystalline  marbles 177 

Origin  and  character 177 

Chemical  composition 177 

Geological  distribution 178 

Geographic  distribution 179 

Production 179 

References 180 

Onyx  marbles 180 

Origin  and  character 180 

Uses  and  production 181 

References 181 

CHAPTER  XI.  —  FIELD  EXAMINATIONS  AND  VALUATION  OF 
STONE  PROPERTIES. 

Field  examination  of  stone  properties 182 

Scope  of  reports 182 

Exploration  required 183 

Schedule  for  notes 184 

Points  to  be  examined 185 

Grain 185 

Color 186 

Joints 186 

Impurities . 187 

Segregations  and  dikes 187 

Weathering 188 

Valuation  of  stone  properties 189 

Engineers'  responsibility  for  flotations 189 

Present  status  of  the  stone  industry 190 

Average  costs  and  profits 190 

Financing  of  the  future 191 

Characteristics  of  industrial  bonds 191 

Raw  materials  as  a  basis  for  bond  issues 192 

Stock  issues  against  quarry  projects 193 

CHAPTER  XII.  —  LABORATORY  TESTING   OF  STONE. 

Trend  of  testing  methods 195 

Data  required  from  tests 196 

Classes  of  tests  applied 197 

I.   Tests  to  determine  composition  and  structure 197 

Chemical  tests 197 

Microscopic  examination 198 

II.   Tests  to  determine  density 198 

Specific  gravity,  weight  and  porosity 198 


Xll  TABLE  OF  CONTENTS 

PAGE 

Interrelation  of  these  properties 198 

Methods  of  determining  weight  per  cubic  foot 200 

Porosity 201 

Value  of  density  tests 201 

III.  Tests  to  determine  durability 202 

Expansion  from  temperature  changes 202 

Absorption 203 

Frost  tests 203 

The  Brard  test  with  sodium  sulphate 205 

Resistance  to  acids 207 

Resistance  to  fire 210 

IV.  Tests  to  determine  strength 214 

Crushing  strength 214 

Transverse  strength 216 

Hardness 216 

List  of  references  on  testing  of  stone 216 

PART   II. —  CLAYS. 

CHAPTER   XIII. —  CLAYS:    GENERAL   CLASSIFICATION. 

Definition  of  clay,  shale  and  slate 218 

Origin  of  clays:  general  statement 219 

Classification  based  on  origin 219 

(a)  Residual  clays 219 

(b)  Transported  clays 220 

CHAPTER   XIV.  —  RESIDUAL   CLAYS. 

Origin  of  residual  clays 221 

Residual  from  decay  of  igneous  rocks 221 

Residual  from  decay  of  shales  or  slates 224 

Residual  from  decay  of  limestone 227 

CHAPTER   XV.  —  TRANSPORTED   CLAYS. 

Origin  of  transported  clays 231 

Water-borne  or  sedimentary  clays 231 

Marine  clays 231 

Marine  clays  proper 231 

Shales 232 

Slates 233 

Stream  clays 233 

Lake  clays 234 

Ice-borne  or  glacial  clays 234 

Wind-borne  or  eolian  clays 234 

List  of  references  on  origin  of  clays 236 

CHAPTER   XVI.  —  DISTRIBUTION  OF  CLAYS. 

Geographic  distribution  of  clays 238 

List  of  references  on  distribution  of  clays 24Q 


TABLE  OF  CONTENTS  xiii 
CHAPTER   XVH.  —  FIELD   EXAMINATION   OF   CLAY  DEPOSITS. 

PAGE 

General  conduct  of  field  work 244 

Use  of  geological  reports 244 

Effect  of  kind  of  clay  on  methods  of  work 245 

Examination  of  shale  deposits 247 

Examination  of  soft  clay  deposits 247 

Dealing  with  known  deposits 248 

Methods  of  boring 249 

The  auger  in  light  work 249 

The  auger  in  heavy  work 252 

References  on  methods  of  field  examination 257 

Determination  of  composition  and  tonnage 257 

Errors  in  sampling 257 

Estimation  of  tonnage 258 


LIST  OF  ILLUSTRATIONS 


FIQ.  PAGE 

1.  CONVENTIONAL  SYMBOLS  FOR  ROCK-CLASSES 7 

2.  ANGLE  OP  DIP  IN  STRATA 12 

3.  SYNCLINE  AND  ANTICLINE 13 

4.  FOLDS  WITH  INCLINED  AXES 13 

5.  COMPRESSED  FOLDS 13 

6.  ORIGIN  OF  THRUST  FAULTS 14 

7.  FAULTS  IN  STRATA 14 

8.  JOINT  PLANES 15 

9.  GRANITE  Boss 18 

10.  LACCOLITH  AND  INTRUDED  SHEETS 19 

11.  VOLCANIC  NECK,  CONE  AND  SURFACE  FLOW 20 

12.  DIKES  AND  SHEET  OF  IGNEOUS  ROCK 20 

13.  DIKES  MADE  PROMINENT  BY  WEATHERING 21 

14.  LAMINATION  AND  JOINT  PLANES  IN  GNEISS 38 

15.  SHEET  STRUCTURE  IN  GRANITE 40 

16.  COLUMNAR  STRUCTURE  OF  TRAP 71 

17.  SLATE  DRESSING;  THE  DRESSING  SHANTIES 116 

18.  SLATE  DRESSING;   BEGINNING  OF  SCULPING 116 

19.  SLATE  DRESSING;   SCULPING 117 

20.  SLATE  DRESSING;  SPLITTING 118 

21.  METHOD  OF  LAYING  ROOF  SLATES 119 

22.  CONCENTRIC  WEATHERING  OF  GRANITE 187 

23.  BOULDERS  FROM  DECAY  OF  IGNEOUS  ROCK 188 

24.  INCLINED  SHALE  BED,  WEATHERED  TO  CLAY 225 

25.  INTERBEDDED  SHALES  AND  LIMESTONES 226 

26.  EFFECT  OF  WEATHERING  ON  INTERBEDDED  SHALES.  4 226 

27.  HORIZONTAL  BEDS  OF  SHALE-CLAY 226 

28.  FORMATION  OF  RESIDUAL  CLAY  FROM  LIMESTONE 228 

29.  RESIDUAL  CLAYS  FROM  CHALK 228 

30.  RESIDUAL  CLAYS  FROM  LIMESTONE 229 

31.  RIVER  TERRACES 233 

32.  CLAY  TERRACES  ALONG  HUDSON  RIVER 235 

33.  PHYSIOGRAPHIC  REGIONS  OF  EASTERN  UNITED  STATES 239 

34.  BASIN  DEPOSIT  OF  CLAY 245 

35.  INTERBEDDED  SANDSTONES  AND  SHALE-CLAYS 246 

36.  BASIN  OR  LENS-SHAPED  CLAY  DEPOSIT 248 

37.  EXAMINATION  OF  TERRACE  DEPOSIT  OF  CLAY 253 

x  v 


BUILDING  STONES  AND  CLAYS 


PART    I.     BUILDING    STONES. 


CHAPTER  I. 
THE   ORIGIN   AND   STRUCTURE   OF  ROCKS. 

The  Engineering  Applications  of  Geology.  —  The  geology  of  a 
region  bears  upon  the  work  of  the  engineer  in  three  different  ways, 
through  its  influence,  respectively,  on  the  topography,  structure 
and  materials  of  the  given  area. 

(1)  The  topography  of  the  district,  on  which  depends  the  loca- 
tion of  both  drainage  lines  and  transportation  routes,  is  directly 
related  to  the  geologic  history  of  the  area. 

(2)  The  underground  structure  determines  the  accessibility  of 
industrially  valuable  mineral  deposits,  as  well  as  the  occurrence 
of  underground  water  supplies. 

(3)  The  rocks  and  minerals  present  in  any  given  area  will 
usually  contribute,  either  directly  or  indirectly,  to  the  supply  of 
materials  available  for  structural  work,  and  for  other  purposes. 

With  these  facts  in  view,  it  is  evident  that  the  relations  to 
engineering  of  structural  and  economic  geology  are  very  intimate. 
In  the  present  volume,  which  deals  with  two  of  the  more  im- 
portant groups  of  structural  materials  used  by  the  engineer,  we 
are  concerned  chiefly  with  a  study  of  the  manner  in  which  certain 
raw  materials  have  been  made  available  for  use.  Before,  how- 
ever, taking  up  these  particular  raw  materials  in  detail,  it  will 
be  well  to  briefly  summarize  the  main  features  of  what  may  for 
convenience  be  termed  Engineering  Geology. 

Outline  of  Earth  History.  —  For  our  present  purposes  it  is 
sufficiently  accurate  to  assume  that  the  earth,  in  the  earliest 
stage  of  its  history  requiring  consideration,  was  a  fused  mass, 
of  approximately  spherical  shape,  cooling  slowly  from  the  ex- 
terior inwards,  and  surrounded  by  an  envelope  of  gases.  When 
the  cooling  had  progressed  far  enough,  the  earth's  exterior  and 

1 


2  BUILDING   STONES   AND  CLAYS 

center  solidified  gradually  —  a  surface  or  crust  of  igneous  rocks 
being  formed  —  while  local  differences  in  the  rate  of  cooling 
caused  irregularities  in  this  surface.  Combinations  of  the  cool- 
ing gases  caused  the  precipitation  of  water,  in  the  form  of  rain; 
and  with  the  action  of  the  first  surface  water  began  the  formation 
of  the  sedimentary  rocks.  The  fallen  rain  gathered  in  slight 
depressions  of  the  crust  to  form  the  earliest  streams  and  rivers; 
and  followed  these  courses  to  deeper  depressions  which  formed 
the  earliest  seas  and  oceans.  In  its  course  the  water,  whether 
raindrop  or  stream,  carried  off  small  portions  of  the  rocks  it 
encountered,  transporting  them  either  mechanically  or  in  solu- 
tion, and  depositing  them  finally  as  sediments.  This  process 
has  continued  to  the  present  day,  a  steady  supply  of  detritus 
being  carried  to  the  seas;  and  it  is  obvious  that  some  counter- 
balancing process  must  act  to  prevent  all  the  lands  being  worn 
down  to  sea  level.  This  compensatory  action  is  evidenced  by 
the  gradual  depression,  at  intervals,  of  portions  of  the  sea  bottom 
(overloaded  with  deposits  of  sediment)  and  the  consequent  rela- 
tive elevation  of  the  land  areas.  The  process  is  therefore  con- 
tinuous, forming  a  regular  three-phase  cycle,  the  phases  being 
(1)  erosion  of  high  lands  by  running  water;  (2)  deposition  of  the 
resulting  detritus  on  the  sea  bottom;  (3)  overloading  and  con- 
sequent depression  of  parts  of  the  sea  bottom  with  a  corre- 
sponding relative  elevation  of  the  land  and  the  recommencement 
of  erosion. 

At  intervals  in  the  earth's  history  these  regular  cyclical  changes 
have  been  aided  or  retarded  by  less  regular  occurrences.  Masses 
of  fused  rock  have  been  forced  up  from  the  interior  to  cool  at  or 
near  the  surface;  heat  and  pressure  have  caused  great  changes 
in  deeply  buried  rock  masses;  minor  movements  in  the  crust 
have  caused  folds,  faults  and  joints  in  the  rock  series;  and  once 
at  least  temperature  changes  have  caused  a  glacial  period  in  the 
temperate  zone.  So  far  as  these  phenomena  concern  the  engi- 
neer they  will  be  discussed  in  later  paragraphs. 

Life  was,  so  far  as  known,  existent  before  the  formation  of  our 
earliest  identified  sedimentary  rocks.  Through  the  following 
ages  it  has,  however,  greatly  changed  in  form  and  type;  and  this 
gradual  evolution  in  living  organisms  aids  in  determining  the 
relative  ages  of  the  rocks  in  which  their  fossil  remains  are  now 
inclosed. 


THE  ORIGIN  AND  STRUCTURE  OF  ROCKS  3 

Relative  Age  of  Rocks.  —  The  geologist,  confronted  with  a 
finished  product  —  a  given  tract  of  country  —  endeavors  to 
work  out  its  history.  Usually  the  first  step  in  this  direction  will 
be  to  map  the  areas  covered  by  different  kinds  of  rock,  but  along 
with  this  areal  mapping  he  must  carry  on  studies  to  determine 
the  relative  age  of  the  various  rock  formations  which  occur  within 
the  limits  of  the  tract  under  consideration.  In  doing  this  the 
following  criteria  are  of  most  service. 

(a)  Superposition.  —  Since  sedimentary  rocks  are  surface  de- 
posits, it  is  obvious  that  of  two  series  of  sedimentary  rocks,  the 
overlying  series  must  be  the  younger,  provided  that  no  serious 
earth  movements  have  altered  their  relative  position  since  they 
were  deposited. 

(b)  Contained   Fragments.  —  If  one  rock  formation  contains 
pebbles  or  other  fragments  of  material  evidently  derived  from 
another  formation,  the  fragment-containing  bed  must  have  been 
formed  after  the  other  had  been  deposited. 

(c)  Contained  Fossils.  —  This,  which  is  usually  the  most  exact 
and  positive  criterion  of  all,  is  not  immediately  evident  like  the 
preceding  two.     In  the  progress  of  geologic  science,  it  has  been 
determined  that  beds  of  certain  age  are  characterized  by  certain 
assemblages  of  fossil  remains.     Comparison  of  the  fossils  found 
in  the  beds  of  the  area  under  study  with  those  found  in  some  area 
where  the  succession  is  already  known,  will  therefore  fix  the 
relative  position  and  age  of  the  series  under  study. 

Geologic  Chronology.  —  By  the  careful  application  of  the 
criteria  briefly  described  in  the  preceding  section,  a  fairly  com- 
plete geologic  chronology  has  been  gradually  worked  out  to 
cover  the  whole  extent  of  earth  history.  For  convenience  of 
reference  and  comparison,  all  of  geologic  time  is  primarily  divided 
into  twelve  periods,  which  in  turn  are  subdivided  into  epochs. 
Still  more  minute  subdivisions  are  stages,  while  the  final  unit  of 
division  is  the  formation. 

This  system  of  subdivision  gives  a  series  of  time  intervals  which, 
taken  together,  cover  all  geologic  history.  The  names  of  the 
periods  are  given  below  in  order  downward  from  the  most  recent 
(Quaternary)  to  the  earliest  (Archaean).  In  a  few  cases  the 
subdivisions  into  epochs  are  also  given. 


BUILDING  STONES  AND  CLAYS 

Period  Epoch 

[Quaternary  ..........  | 

Cenozoic  .....  •<  f  Pliocene 

Tprtiarv  J  Miocene 

|/ertiary  ............  1  Oligocene 

t  Eocene 
f  Cretaceous 
Mesozoic  ......  «j  Jurassic 

iTriassic 

f  Permian 
Carboniferous  .......  •<  Pennsylvanian  or  Coal  Measures 

(^  Mississippian  or  Subcarboniferous 


Devonian 
Silurian 
Ordovician 
Cambrian 


Paleozoic 


Pre-Cambrian 


To  the  engineer  the  determination  of  the  geologic  age  of  the 
rocks  of  any  given  district  is  rarely  a  matter  of  importance, 
except  in  so  far  as  geologic  age  may  affect  the  character  of  the 
mineral  products.  It  would  be  folly,  for  example,  to  expect  to 
find  important  workable  deposits  of  coal  in  rocks  older  than 
the  Carboniferous  period  —  but  that  is  about  the  only  valuable 
general  statement  that  can  be  made.  In  any  particular  small 
area,  of  course,  a  relation  between  age  and  material  is  more 
common.  The  valuable  "  cement  rock"  of  the  Lehigh  district 
of  Pennsylvania,  for  example,  occurs  in  that  region  only  in  beds 
of  one  particular  geologic  age,  and  it  would  be  useless  to  search 
for  it  in  rocks  of  other  periods.  Another  case  in  point  is  the  red 
or  fossil  iron  ore,  so  important  to  the  southern  iron  industry. 
This  occurs  in  the  eastern  United  States  only  in  rocks  of  Clinton 
age,  and  the  presence  or  absence  of  the  ore  on  any  particular 
property  can  therefore  be  inferred  on  purely  geologic  grounds. 
In  Luxembourg,  however,  an  entirely  similar  ore  occurs  in  rocks 
of  much  later  age  —  so  that  it  is  evident  that  such  a  generaliza- 
tion is  safe  only  within  rather  close  geographic  limits. 

The  Geologic  Viewpoint.  —  It  is  not  at  all  difficult  for  an  engi- 
neer, confronted  with  some  semi-geologic  problem,  to  master  in 
a  short  time  the  principal  geologic  facts  to  which  he  must  give 
consideration.  That  is  merely  a  matter  of  application  to  a 
rather  interesting  study.  What  is  difficult,  however,  is  for  him 
to  learn  to  look  at  these  facts  from  what  may  be  termed  the 
geologic  viewpoint. 


THE  ORIGIN  AND  STRUCTURE  OF  ROCKS  5 

To  judge  from  published  reports  on  water-supply  problems 
and  other  work  involving  engineering  geology,  the  tendency  is 
to  assume  unconsciously  that  in  considering  geologic  facts  it  is 
useless  to  apply  the  same  type  and  closeness  of  reasoning  which 
are  essential  to  the  solution  of  purely  engineering  problems. 
The  effect  of  this  mistaken  attitude  is  that  the  engineer  too  often 
is  inclined  to  invoke  forces  and  agencies  totally  unknown  to 
engineering  practice  in  order  to  aid  in  solving  a  geologic  problem ; 
so  that  the  finished  report  is  frequently  a  curious  mixture  of  clear 
observation  and  erroneous  interpretation. 

In  considering  this  matter  the  engineer  will  avoid  many  serious 
misinterpretations  of  facts  if  he  bears  in  mind  that:  — 

(a)  Geologic  occurrences  are  to  be  explained  by  reference  to 
the  same  physical  forces  which  are  now  in  operation  —  running 
water,  winds,  frost,  terrestrial  heat,  etc. 

(6)  These  forces  have,  on  the  whole,  always  been  of  about  the 
same  degree  of  intensity;  the  one  prominent  exception  being 
the  extension,  during  the  glacial  period,  of  intense  ice  action  into 
the  temperate  zone. 

(c)  Changes  in  the  earth's  surface  —  whether  of  coast  line, 
relief,  or  drainage  —  have  been  almost  invariably  brought  about 
with  extreme  slowness. 

(d)  Gorges,  canyons,  mountain  ranges  and  other  striking  physi- 
cal features  are  therefore  due  almost  always  to  the  long  continued 
action  of  ordinary  familiar  physical  forces,  and  not  to  sudden 
and  violent  "upheavals,"  "volcanic  outbursts"  or  other  "con- 
vulsions of  nature." 

Kinds  of  Rocks.  —  Rocks  are  classified,  according  to  origin,  in 
one  of  two  groups:  (1)  igneous,  or  (2)  sedimentary.  In  by  far 
the  majority  of  cases  there  is  no  difficulty  in  determining  the 
group  in  which  any  given  rock  should  be  placed;  but  at  times 
the  decision  is  more  difficult  and,  in  some  cases,  impossible. 

(1)  The  igneous  rocks  are  those  which  have  been  formed  by 
the  cooling  of  fused  material.  The  original  crust  of  the  earth 
was  of  course  formed  entirely  of  igneous  rocks,  but  it  is  highly 
improbable  that  any  of  this  original  crust  is  now  exposed  at  the 
earth's  surface.  The  igneous  rocks  with  which  we  have  to  deal 
are  of  later  origin,  being  derived  from  molten  material  which 
at  different  periods  has  been  forced  up  through  and  into  other 
rocks.  In  most  cases  this  molten  rock  did  not  reach  the  surface 


6  BUILDING  STONES   AND   CLAYS 

while  fused,  but  cooled  and  solidified  slowly  while  covered  by 
thick  masses  of  overlying  material,  and  is  now  exposed  to  view 
owing  to  the  slow  removal  of  this  covering. 

(2)  The  sedimentary  rocks  are  those  derived  from  the  decay 
of  preexisting  strata,  the  material  so  obtained  being  carried 
(usually  by  water)  in  suspension  or  solution  to  some  point  where 
it  is  redeposited  as  a  bed  of  sand,  clay  or  limestone.  Subse- 
quently this  loosely  deposited  material  may  become  consolidated 
and  hardened  by  pressure  or  other  agencies,  the  result  being  the 
formation  of  sandstones,  shales  and  slates  from  the  original 
unconsolidated  beds  of  sand  and  clay. 

In  the  later  chapters  of  this  volume,  which  deal  respectively 
with  the  igneous  rocks  and  the  sedimentary  rocks,  further  data 
will  be  presented  on  the  characters,  origin  and  subclassification 
of  each  of  these  groups. 

Metamorphism  of  Rocks.  —  All  rocks  are  more  or  less  changed 
or  metamorphosed  from  the  condition  in  which  they  were  first 
deposited  (in  the  case  of  sedimentary  rocks)  or  in  which  they 
first  cooled  from  fusion  (in  the  case  of  igneous  rocks).  The 
changes  are  due  to  the  action  of  heat,  pressure  and  chemical 
agencies;  and  the  effects  may  appear  in  changes  of  either  the 
physical  structure  of  the  rock,  its  texture  or  its  chemical  com- 
position. 

As  has  been  said,  all  rocks  have  suffered  such  changes  or  meta- 
morphism  to  a  greater  or  lesser  extent,  but  the  term  metamorphic 
rocks  is  restricted  properly  to  the  rocks  in  which  the  changes 
have  gone  so  far  as  to  produce  very  marked  alterations,  some- 
times entirely  obliterating  the  original  structure,  and  at  times 
rendering  it  difficult  or  even  impossible  to  decide  whether  the 
original  rock  was  of  sedimentary  or  of  igneous  origin. 

Conventional  Symbols  for  Rock  Classes.  —  In  representing 
the  different  classes  of  rocks  on  geologic  cross  sections,  it  is  often 
necessary  to  adopt  different  symbols  or  patterns  so  as  to  dis- 
tinguish between  igneous  rocks,  shales,  limestones,  etc.  Though 
these  symbols  are  purely  conventional,  there  is  a  great  advantage 
in  having  the  same  symbols  adopted  by  every  one  for  the  same 
rocks,  and  considerable  uniformity  in  this  regard  can  now  be 
seen  in  the  publications  of  the  various  geological  surveys. 

In  Fig.  1,  the  patterns  for  the  different  classes  of  rocks  by  the 
United  States  Geological  Survey  are  shown. 


THE  ORIGIN  AND  STRUCTURE  OF  ROCKS 


II.        I 


Limestones. 


Shales. 


Shaly  limestones. 


Sandstones  and  con- 
glomerates. 


Shaly  sandstones. 


Calcareous  sandstones. 


3fassiye  and  Taedded  igneous  "cocks. 
Fig.  1.  —  Conventional  symbols  for  kinds  of  rock. 


Chemical  Relationship  of  the  Classes  of  Rocks.  —  A  feature  of 
considerable  economic  and  scientific  interest  appears  to  have  been 
overlooked  by  geologists  as  well  as  by  engineers.  This  is  the 
relationship  which  exists  between  the  chemical  composition  of 
the  various  classes  of  rocks.  It  is  well  brought  out  in  the  follow- 
ing table,  which  was  prepared  by  combining  data  published  by 
Professor  F.  W.  Clarke  and  by  the  present  writer. 

It  will  be  seen  that  this  table  gives  average  analyses  of  large 
series  of  different  rock  groups,  and  the  averages  may  therefore 
be  considered  to  fairly  represent  the  mean  composition  of  these 
groups.  Examination  of  the  table  shows  that  the  average 
igneous  rock  is  closely  similar  in  composition  to  the  average  shale 
and  the  average  slate.  In  other  words,  the  shales  and  slates  are 
made  up  of  fine  particles  of  the  same  materials  which  occur  in 
the  igneous  rocks,  and  in  about  the  same  proportions.  Evi- 
dently little  chemical  sorting  or  segregation  took  place  during  the 
formation  of  shales  and  slates.  With  regard  to  the  sandstones 
and  limestones  the  case  is  very  different.  Here  there  has  been 


8 


BUILDING  STONES  AND  CLAYS 


a  great  deal  of  separation,  resulting  in  the  deposition  of  almost 
pure  silica  in  the  case  of  sandstones  and  of  lime  carbonate  in 
limestones. 

TABLE  1.  — AVERAGE  ANALYSES  OF  VARIOUS  CLASSES 
OF  ROCKS. 


830 
Igneous 
rocks. 

78 
Shales. 

36 
Slates. 

371 
Sandstones. 

345 
Limestones 

Silica  (SiO2)  
Alumina  (A12O3)  *  
Ferric  oxide  (Fe2O3)  .... 
Ferrous  oxide  (FeO)  .... 
Lime  (CaO)  .... 

59.71 
16.01 
2.63 
3.52 
4  90 

58.38 
16.12 
4.03 
2.46 
3  12 

60.64 
18.05 
2.25 
3.66 
1  54 

84.86 
6.37 
1.39 
0.84 
1  05 

5.19 
0.87 
0.54 
n.d. 
42  61 

Magnesia  (MgO)  

4  36 

2.45 

2  60 

0  52 

7.90 

Soda  (Na2O)  

3.55 

1.31 

1.19 

0.76 

0.05 

Potash  (K2O) 

2  80 

3  25 

3  69 

1  16 

0  33 

Combined  water  .  . 

1  52 

3  68 

3  51 

1  47 

0  56 

Moisture  

1  34 

0  62 

0  27 

0  21 

*  Including  small  amounts  of  titanic  oxide  (TiO2). 

In  the  case  of  such  sedimentary  rocks  as  the  sandstones  and 
shales,  the  entire  process  is  a  purely  mechanical  matter,  the 
materials  being  carried  in  suspension  by  moving  water,  and  being 
deposited  because  of  decrease  in  the  velocity  of  the  water  which 
has  transported  them. 

The  limestones,  however,  present  a  more  complicated  case, 
for  the  lime  and  magnesium  carbonates  of  which  they  are  formed 
are  usually  carried  in  solution  by  water,  and  are  deposited  by 
chemical  or  organic  agencies.  These  differences  in  origin  and 
deposition  will  be  taken  up  in  more  detail  in  later  chapters, 
where  the  various  kinds  of  sedimentary  rocks  are  separately 
discussed. 

Genetic  Relationship  of  the  Rock  Classes.  —  It  may  aid  the 
reader  to  comprehend  more  fully  the  closely  interwoven  relation- 
ships of  the  various  classes  of  rocks  if  the  discussion  be  carried 
a  stage  further,  and  some  consideration  given  to  their  relation- 
ship so  far  as  origin  is  concerned.  So  far  as  known  to  the  writer, 
the  matter  which  is  here  presented  has  never,  even  in  purely 
geologic  treatises,  been  set  forth  in  a  closely  analytical  form, 
though  of  course  the  ideas  which  underlie  this  analysis  are 
generally  accepted. 


THE  ORIGIN  AND  STRUCTURE  OF  ROCKS  9 

The  accompanying  diagrammatic  table  (Table  2)  has  been 
prepared  to  serve  as  a  convenient  semigraphic  summary  of  the 
statements  in  the  following  paragraphs,  and  should  consequently 
be  studied  in  connection  with  those  paragraphs.  In  order  to 
facilitate  this  cross  reference,  the  notation  used  in  the  table  has 
also  been  employed  to  designate  the  corresponding  steps  in  the 
more  detailed  discussion  below. 

I.  For  our  present  purpose  it  will  be  sufficiently  exact  to  con- 
sider that,  in  the  earliest  stage  to  which  we  need  refer,  the  earth's 
crust  was  already  solidified  by  cooling,  and  that  it  was  composed 
entirely  of  igneous  rocks.     These  rocks  intergraded  closely  in 
composition,  but  for  convenience  here  may  be  divided  into  an 
acid   group  (I  a)  and   a   basic   group    (I  6).     The   acid  group 
would  include  those  rocks  higher  in  silica  than  the  average  noted 
on  page  8,  while  the  basic  rocks  would  include  those  lower  in 
silica  than  the  average.     The  dividing  line  between  the  two 
groups  is  therefore  fixed  naturally  at  about  59  per  cent  silica. 

II.  The  igneous  rocks  forming  the  exposed  portion  of  the  crust 
were  almost  immediately  attacked  by  both  mechanical  and  chemi- 
cal agencies  of  destruction.     The  two  sets  of  agents  undoubtedly 
commenced  their  destructive  action  almost  simultaneously,  but 
it  will  be  logically  exact  and  certainly  conducive  to  clearness 
in  the  present  discussion  if  we  at  first  consider  only  the  effects 
of  purely  mechanical  attack  on  the  exposed  crustal  rocks. 

The  effect  of  heat  and  cold,  rain  and  running  water,  on  a  series 
of  rocks  is  to  ultimately  effect  the  mechanical  disintegration  of 
a  portion  of  the  exposed  outcrop.  The  material  thus  broken 
down  mechanically  is  carried  off  by  running  water  and  finally 
deposited.  Since  it  is  assumed  that  this  entire  process  has  not 
been  assisted  by  chemical  action,  and  that  the  material  deposited 
has  not  been  subjected  to  mechanical  concentration  or  sorting, 
the  ultimate  result  would  be  the  formation  of  a  bed  of  sandy 
clay.  In  composition  this  clay  would  not  differ  greatly  from 
the  average  composition  of  the  igneous  rock  from  which  its 
materials  were  derived.  The  clays  thus  formed  would  be  either 
typically  siliceous  clays  (II  a)  or  basic  clays  (II  6)  according  to 
the  character  of  the  particular  igneous  rocks  from  which  they 
were  derived. 

III.  As  a  matter  of  fact,  however,  both  leaching  and  sorting 
must  have  taken  place  at  an  early  period  in  the  history  of  the 


10 


BUILDING  STONES  AND  CLAYS 


sedimentary  rocks.  The  principal  sorting  effect  would  be  the 
mechanical  separation  of  the  particles  of  quartz  from  the  other 
residual  material,  owing  to  the  greater  resistance  of  quartz  to 
both  mechanical  and  chemical  attack.  The  sorting  out  of  this 
quartz  and  its  separate  deposition  would  give  rise  to  the  for- 
mation of  beds  of  sand  and  gravel  (IIIc).  The  principal  effect 
of  chemical  attack  would  be  the  removal  of  lime  in  solution. 
The  lime  thus  carried  off  would  be  redeposited,  either  through 
direct  chemical  action  or  by  the  agency  of  living  organisms,  to 
form  marl  deposits,  shell  beds,  etc.  (Hid). 


TABLE  2.  — STAGES  IN  THE  ORIGIN  OF  ROCK  CLASSES. 


Stages  of  origin. 

Siliceous. 

Silico-aluminous. 

Calcareous. 

I.  Original  con- 
stituents of  the  earth's 
crust. 

la.   Acid 
rocks 

1  6.    Basic 
rocks 

II.  Derived  from  I 
by  mechanical  erosion 
and  sedimentation 
without  sorting. 

II  a.     Acid 
clays 

116.  Basic 
clays 

III.  Derived  from  I 
or  II,  with  the  aid  of 
mechanical  sorting 
and  chemical  leaching. 

Ill  c.  Beds 
of  sand  and 
gravel. 

Ilia.    Acid 
clays 

III  6.  Basic 
clays 

Hid.  Shell 
beds,  marl 
deposits, 
etc. 

IV.  Derived  from 
III  by  normal  consoli- 
dation. 

IV  c.  Sand- 
stones 

IV  a.    Acid 
shales 

IV  b.  Basic 
shales 

IV  d.  Lime- 
stones 

V.  Derived  from  IV 
by  metamorphism. 

Vc.  Quart  z- 
ites 

Va.   Acid 
slates 

V6.  Basic 
slates 

Vd.  Marbles 

The  mechanical  removal  of  silica  and  the  chemical  removal 
of  lime  would  leave  the  balance  of  the  residual  material  still  in 
the  class  of  clays,  as  III  a,  and  III  6,  but  somewhat  poorer  in 
silica,  lime  and  other  soluble  constituents  than  if  such  sorting 
and  leaching  had  not  taken  place. 

IV.  The  deposits  thus  far  considered  are  still  to  be  regarded 
as  relatively  unconsolidated  beds  of  material.  As  these  beds 
were  covered  by  later  rocks,  pressure,  heat  and  renewed  chemical 
action  were  gradually  brought  into  play.  The  result  was  that 


THE  ORIGIN  AND  STRUCTURE  OF  ROCKS  11 

the  beds  of  sand  and  gravel  (III  c)  became  ultimately  sandstones 
(IV  c) ;  the  clays  (III  a  and  III  6)  became  shales  (IV  a  and  IV  6) ; 
while  the  calcareous  deposits  (III  d)  became  limestone  (IV  d) . 
No  serious  chemical  change  resulted  from  this  consolidation,  so 
that  the  rocks  of  the  subgroups  of  IV  are  closely  akin  chemi- 
cally to  the  unconsolidated  deposits  of  III  from  which  they  were 
respectively  derived. 

V.  In  most  cases  the  process  of  consolidation  stopped  at  the 
stage  which  has  just  been  discussed,  but  locally  the  consolidating 
agencies  persisted  in  their  work  to  a  point  where  the  physical 
changes  which  they  caused  warrant  us  in  giving  another  name 
to  the  product.  Thus  the  sandstones  (IV  c),  if  consolidated 
very  intensely,  might  locally  become  quartzites  (V  c) ;  the  shales 
(IV  a  and  IV  6)  in  places  became  slates  (V  a  and  V  6) ;  and  the 
limestones  (IV  d)  in  metamorphic  regions  became  marbles  (V  d) . 
In  these  further  consolidations  the  chemical  changes  which  take 
place  are  very  slight  as  compared  with  the  purely  physical 
alterations. 

THE  STRUCTURES   OF  ROCKS. 

Under  this  heading  will  be  discussed  such  structural  features 
as  are  common  to  all  classes  of  rocks.  Structures  peculiar  to 
the  igneous  rocks  will  be  considered  in  Chapter  II,  while  those 
peculiar  to  the  sedimentary  rocks  will  be  discussed  in  Chapter  VI. 

As  thus  limited,  the  structural  conditions  to  be  considered  in 
the  present  section  include  the  inclination  of  beds  (dip,  strike, 
etc.);  rock  folding;  faults;  jointing  and  cleavage. 

Inclination  of  Beds;  Dip  and  Strike.  —  The  beds  of  sedimen- 
tary rocks,  having  been  formed  for  the  most  part  by  deposition 
on  the  gently  sloping  bottoms  of  bodies  of  water,  would  naturally 
have  a  horizontal  or  nearly  horizontal  attitude  at  the  time  of 
their  formation.  But  during  the  numerous  elevations  and  de- 
pressions of  the  land  which  have  occurred  since  their  deposition, 
this  original  horizontality  of  bedding  was  in  many  cases  de- 
stroyed, so  that  now  we  may  find  sedimentary  rocks  whose  beds 
are  inclined  at  all  angles  to  the  horizontal.  This  is  particularly 
true  in  the  Appalachian,  Lake  Superior,  Rocky  Mountain  and 
Pacific  Coast  regions,  where  horizontal  strata  are  the  exception 
rather  than  the  rule.  In  the  central  United  States,  however, 
most  of  the  rocks  still  lie  almost  or  quite  horizontal,  an  inclina- 


12  BUILDING  STONES  AND  CLAYS 

tion  of  over  five  degrees  being  distinctly  uncommon  in  the  States 
of  the  Mississippi  basin. 

In  describing  the  attitude  of  a  bed  inclined  to  the  horizon,  it 
is  necessary  to  do  so  in  terms  of  dip  and  strike;  which  requires 
that  these  two  terms  be  defined.  The  strike  of  an  inclined  bed 
may  be  roughly  defined  as  the  direction  or  trend  of  the  bed.  To 

be  more  precise,  it  is  the  compass  bearing 
of  a  straight  line  drawn  horizontally  on 
one  of  the  faces  of  the  bed.  The  dip 
of  the  bed  is  the  angle  made  with  the 
horizontal  by  a  line  drawn  on  the  sur- 
face of  the  bed,  at  right  angles  to  the 
strike  (Fig.  2).  Since  the  two  factors 
are  thus  related,  it  is  unnecessary  to 

give  the  exact  compass  bearing  of  the  dip  (for  that  will  always 
be  at  right  angles  to  the  strike)  but  merely  the  quadrant.  In 
description  it  is  therefore  sufficient  to  say,  for  example,  that  a 
rock  has  a  strike  of  N.  30°  E.,  dip  35°  S.  E.  —  which  can  readily 
be  seen  to  imply  that  the  dip  of  35  degrees  is  in  the  direction 
S.  60°  E. 

Though,  from  a  very  strict  standpoint,  the  terms  dip  and  strike 
would  be  applicable  only  in  describing  the  bedding  planes  of 
sedimentary  rocks,  there  is  no  real  reason  for  not  using  them  in 
describing  the  attitude  of  the  laminated  igneous  rocks  (gneisses, 
schists,  etc.),  and  they  are  commonly  so  applied. 

Rock  Folds.  —  The  terms  dip  and  strike  having  been  defined, 
it  is  possible  to  glance  at  certain  broader  features  of  rock  struc- 
ture of  which  dip  and  strike  are  merely  local  manifestations. 
These  broader  features  are  connected  with  the  subject  of  rock 
folding. 

In  the  course  of  earth  movements,  folds  and  flexures  of  various 
types  are  developed  in  beds  of  rock  which  may  previously  have 
been  horizontal.  If  the  movement  simply  elevates  or  depresses 
one  side  of  an  area,  so  that  as  a  result  the  rocks  everywhere  dip 
in  the  same  direction,  the  resulting  attitude  of  the  rocks  is  called 
a  monocline.  If,  however,  compressive  or  tensile  stresses  accom- 
pany the  uplift  or  depression,  a  complete  fold  of  some  sort  will 
be  formed. 

When  a  complete  fold  is  presented  for  observation,  it  may  be 
either  a  syncline  or  trough,  in  which  the  strata  on  both  sides  dip 


THE  ORIGIN  AND  STRUCTURE  OF  ROCKS 


13 


toward  the  axis  of  the  fold;  or  an  anticline  or  arch,  in  which  the 
strata  on  both  sides  dip  away  from  the  axis  of  the  fold.     Fig.  3 


Fig.  3.  —  Syncline  and  anticline. 

shows  both  of  these  structures,  a  very  sharp  anticline  being 
shown  at  the  extreme  right  of  the  figure,  while  a  rather  flat 
syncline  occupies  the  remainder  of  the  sketch. 


Fig.  4.  —  Folds  with  inclined  axes. 

In  the  simple  forms  of  these  folds  shown  in  Fig.  3,  the  axes  of 
the  folds  are  vertical  in  each  case,  and  there  is  no  particular  com- 
pression of  the  limbs  of  the  folds.     In  more  complex  cases  we 
find  folds  with  inclined  axes, 
as  is  shown  by  those  repre- 
sented in  Fig.  4;  or  with  ex- 
tremely compressed  limbs  as 
shown  in  Fig.  5. 

Faults  in  Strata.  —  When, 
in  the  course  of  earth  move- 
ments, the  strata  subjected 
to  stress  are  too  rigid  to 
yield  by  simple  folding,  or 
when  the  stress  is  applied 
too  rapidly,  they  will  yield  by  fracture.  Such  fractures,  which 
may  occur  at  any  point  in  the  stressed  area,  result  in  the  for- 
mation of  a  fault,  which  may  be  considered  simply  as  a  break  in 


/  /  /V: '/'  •'  '  i  7 77'      I '  I ,' 
'1  I  i '•      ///////       //// 


Fig.  5.  —  Compressed  folds. 


14 


BUILDING  STONES  AND  CLAYS 


the  continuity  of  the  strata,  accompanied  by  elevation  or  de- 
pression of  the  beds  on  one  side  of  the  fault  plane. 


Fig.  6.  —  Origin  of  thrust  faults:  a,  overturned  fold  in  rocks,  passing  by  frac- 
ture into  b,  thrust  fault. 

On  a  large  or  small  scale,  faulting  is  a  very  common  phenome- 
non, particularly  in  regions  of  intense  folding.  It  is  a  matter  of 
peculiar  economic  importance  to  the  mining  engineer,  since  the 
existence  of  faults  in  a  district  complicates  the  underground 
structure,  and  renders  it  difficult  to  follow  out  a  mineral  deposit 
affected  by  faulting.  For  our  present  purposes,  however,  the 
subject  of  faulting  requires  little  consideration,  for  no  engineer 
would  consider  opening  a  structural  stone  quarry  in  a  badly 
faulted  area.  On  the  other  hand,  the  existence  of  numerous 
faults  might  be  a  distinct  advantage  in  operating  a  quarry  for 
crushed  stone. 


Fig.  7.  —  Faults  in  strata:  a,  original  attitude  of  strata;   6,  position  after 
normal  faulting;  c,  position  after  reverse  faulting. 

Joints.  —  A  sedimentary  rock,  as  originally  deposited,  would 
probably  show  more  or  less  distinct  bedding  planes  (see  page  93), 
and  would  have  a  tendency  to  break  or  split  parallel  to  these 
planes.  But  it  would  not  have  any  planes  of  easy  fracture 
transverse  to  the  bedding  planes,  for  in  this  direction  the  stone 
would  be  entirely  homogeneous  and  massive.  Igneous  rocks, 
cooled  entirely  without  interference,  would  be  even  more  homo- 


THE  ORIGIN  AND   STRUCTURE  OF  ROCKS 


15 


geneous;  and  would  not  show  planes  of  easy  fracture  in  any 
direction. 

As  a  matter  of  fact,  however,  both  sedimentary  and  igneous 
rocks  do  commonly  show  certain  planes  (entirely  distinct  from 
the  bedding  planes  in  the  case  of  the  sedimentary  rocks),  along 
which  they  break  or  cut  with  greater  ease  than  in  any  other 
direction.  When  these  planes  are  so  marked  as  to  show  on  the 
surfaces  of  the  rock,  dividing  it  into  more  or  less  rectangular 


Fig.  8.  —  Joint  planes  in  sandstone.     (Photo  by  E.  M.  Kindle.) 

masses,  they  are  described  as  joints  (Fig.  8) .  When  the  fracture 
planes  do  not  show  on  the  surface,  but  merely  exist  as  planes  of 
weakness  within  the  rock  itself,  we  have  the  rift  and  grain  which 
are  discussed  in  a  later  section  (page  39)  in  describing  the  struc- 
ture of  granites. 

Recurring  to  the  subject  of  jointing,  the  examination  of  a 
quarry  will  show  almost  invariably  that  the  rock  breaks  out  in 
rectangular  or  prismatic  blocks;  and  that  the  surfaces  which 
bound  these  blocks  are  parallel  to  one  or  more  systems  of  joints. 

As  to  origin,  joint  planes  may  be  due  to  cooling  stresses  (in 


16  BUILDING  STONES  AND  CLAYS 

the  case  of  igneous  rocks);  to  drying,  in  the  case  of  sediments; 
or  to  earth  movements  after  deposition,  in  the  case  of  either 
igneous  or  sedimentary  rocks. 


SUGGESTIONS   FOR   GEOLOGIC   READING. 

The  subjects  discussed  in  this  chapter  may  perhaps  be  com- 
pleted most  profitably  by  a  brief  reference  to  a  few  books  dealing 
with  various  phases  of  engineering  geology  in  more  detail  than 
has  been  possible  here.  The  writer  has  no  intention  of  outlining 
a  course  of  geologic  study,  but  will  simply  note  the  lines  along 
which  further  reading  may  be  useful  to  the  engineer  desirous  of 
securing  a  working  acquaintance  with  both  geologic  theory  and 
practice,  so  far  as  they  affect  his  own  work. 

1.  As  to  general  geology,  one  of  the  more  elementary  text- 
books, such  as  those  of  Tarr  or  Brigham,  will  in  most  cases  be 
more  satisfactory  than  a  larger  treatise.     The  best  manual,  of 
course,  is  the  Geology  of  Chamberlin  and  Salisbury,  but  this  is  too 
bulky,  too  detailed  and  too  expensive  to  be  generally  serviceable. 

2.  The  next  stage  is  some  degree  of  acquaintance  with  the 
field  practice  of  geology,  including  knowledge  of  the  facts  which 
should   be   observed   and   of  the   methods  adopted   in  noting, 
recording,  and  interpreting  these  facts.     In  this  field  Geikie's 
Structural  and  Field  Geology  is  still  unsurpassed  as  a  general  guide 
for  field  work;  while  Grenville-Cole's  A  ids  in  Practical  Geology 
contains  valuable  data  relative  to  the  rocks,  minerals,  and  fossils 
which   may   require   determination.     Both   of  these   books   are 
English,  and  therefore  much  of  their  illustrative  matter  will  be 
unfamiliar  to  the  American  reader;  but  in  spite  of  this  drawback 
Geikie's  book  at  least  can  hardly  be  dispensed  with. 

3.  Further  study  of  the  structures  and  classification  of  rocks, 
and  of  the  processes  involved  in  their  origin  and  decay,  will 
fortunately  be  aided  by  two  books  which  are  at  once  readable 
and  authoritative.     Reference  is  here  made  to  Kemp's   Hand- 
book of  Rocks  and  to  Merrill's  Rocks,  Rock  Weathering,  and  Soils. 
The  two  do  not  cover  exactly  the  same  ground,  but  supplement 
each  other  admirably.     Of  the  two,   Kemp's  book  should  be 
taken  up  first,   and  is  probably  of  more  general  service;  but 
Merrill's  volume  has  a  more  direct  bearing  on  the  problems  in- 
volved in  the  weathering  and  decay  of  building  stone. 


CHAPTER   II. 
IGNEOUS  ROCKS  IN   GENERAL. 

IN  the  previous  chapter  the  origin  and  characters  of  the  igneous 
rocks  have  been  briefly  noted,  but  only  as  connected  with  the 
relationships  of  the  various  rock  classes,  and  not  in  the  detail 
required  by  their  industrial  importance.  In  the  present  chapter 
the  more  important  characteristics  common  to  all  igneous  rocks 
will  be  discussed  in  such  detail  as  seems  advisable,  while  the 
special  characteristics  of  the  granites  and  traps  will  be  taken  up 
in  the  later  chapters  in  which  these  two  commercial  subgroups  of 
the  igneous  rocks  are  described. 

Origin  of  Igneous  Rocks.  —  According  to  the  more  commonly 
accepted  theories,  the  entire  earth  was  at  one  time  a  molten 
mass;  and  at  least  part  of  its  interior  is  still  either  fluid  or  on 
the  verge  *  of  fluidity.  The  igneous  rocks,  as  now  found  at  the 
surface,  comprise  the  materials  which  have  solidified  and  crys- 
tallized by  cooling  from  this  state  of  fusion.  The  solid  crust 
first  formed  on  the  cooling  earth  was  of  course  composed  entirely 
of  igneous  rocks,  and  it  is  possible  (though  highly  improbable) 
that  portions  of  this  original  crust  are  still  exposed  at  various 
points  on  the  present  surface  of  the  earth.  Most  of  the  igneous 
rocks,  however,  have  solidified  at  later  periods  of  the  earth's 
history,  having  been  forced  upward  into  or  through  the  over- 
lying rocks,  and  having  passed  upward  until  they  reached  a 
point  at  which  decreased  pressure  and  lowered  temperature  have 
allowed  the  molten  material  to  cease  its  movement,  to  cool  and 
to  crystallize. 

Modes  of  Occurrence  of  Igneous  Rocks.  —  Both  scientific  and 
economic  interest  attach  to  a  study  of  the  modes  in  which  igneo.us 

*  In  explanation  of  this,  it  is  clear  that  the  pressure  of  overlying  rocks  may 
be  sufficient  to  keep  the  interior  in  a  solid  condition,  even  though  the  tempera- 
ture in  the  depths  may  be  above  that  which  would  be  required  to  melt  these 
rocks  if  they  were  at  the  surface.  Under  these  conditions,  any  release  of 
pressure  will,  of  course,  immediately  permit  the  highly  heated  rock  material  to 
become  fluid. 

17 


18 


BUILDING  STONES  AND  CLAYS 


rocks  have  reached  their  present  condition  at  the  earth's  surface, 
so  that  attention  can  properly  be  directed  to  a  brief  discussion 
of  the  principal  modes  of  occurrence. 

For  our  present  purposes,  the  principal  types  which  require 
consideration  are  the  following: 


Fig.  9.  —  Granite  boss  rising  above  limestone  plain.      (Photo  by  E.  C.  EckelJ 

1.  Stratiform  Masses.  —  It  would  of  course  be  incorrect  to 
apply  the  term  "  stratified "  to  igneous  masses,  for  owing  to 
their  origin  the  term  would  be  obviously  a  misnomer.  But  on 
all  the  continents  it  is  found  that  the  Archaean  rocks  are  com- 
posed largely  of  igneous  materials.  These  include  both  basic 
and  acid  rocks,  and  vary  in  structure  from  entirely  massive  to 
thoroughly  gneissoid  types.  It  is  impossible  to  prove  at  present 
that  these  Archaean  igneous  rocks  were  ever  intruded  into  other 
formations.  In  most  cases  all  that  can  be  said  about  their  mode 
of  occurrence  is  that  they  now  exist,  covering  immense  areas  on 
the  earth's  surface,  and  serving  as  a  basement  or  floor  on  which 
the  earliest  known  fossiliferous  rocks  were  deposited.  Because 
of  the  facts  that  they  can  be  separated  into  different  formations, 


IGNEOUS  ROCKS   IN   GENERAL 


19 


that  they  have  no  definite  relation  to  sedimentary  rocks  of  the 
same  date,  and  that  they  are  generally  thoroughly  laminated 
and  folded,  it  is  convenient  to  use  the  term  stratiform  masses  in 
describing  them. 

2.  Batholiths.     Along  the  axes  of  many  mountain  chains  are 
found  vast  masses  of  granitic  and  other  igneous  rocks,  evidently 
intruded  into  existing  sedimentary  deposits,  but  having  cooled  at 
a  considerable  depth  below  the  surface  of  the  earth.     These  cores 
or  batholiths  are  now  exposed  at  the  surface  simply  because  the 
sedimentary  rocks  which  once  overlay  them  have  been  removed 
by  erosion.     Smaller  masses  of  the  same  general  type,  weathered 
out  so  as  to  project  above  the  general  surface  level,  are  referred 
to  as  bosses  or  stocks.     One  of  these  is  illustrated  in  Fig.  9. 

3.  Laccoliths.     The  two  types  of  rock  mass  which  has  been 
discussed  above  agree  in  that  their  cooling  took  place  so  far 
below  the  surface  that  the  nearness  of  the  latter  had  no  effect  on 
the  shape  of  the  mass  or  on  the  texture  of  the  rock.      In  the 
modes  of  occurrence  which  remain  to  be  discussed  this  was  not  the 
case. 


Fig.  10.  —  Laccolith,  with  supply  neck  (A)  and  sheets  (B). 

A  mass  of  heated  igneous  rock,  rising  upward  through  approxi- 
mately horizontal  existing  strata  from  a  molten  reservoir  might 
conceivably  reach  a  point  at  which  it  would  be  easier  to  force 
the  overlying  strata  up  into  a  dome  or  arch  rather  than  to  break 
away  through  them.  The  igneous  rock,  cooling  in  the  arched 
cavity  thus  formed,  would  take  the  form  of  a  laccolith.  In  Fig.  10 
a  typical  laccolith  is  shown  in  cross  section,  together  with  some 
of  the  phenomena  which  usually  accompany  it. 

4.  Volcanic  products.  If  the  igneous  rock  penetrated  to  the 
surface,  and  issued  at  some  particular  point  of  weakness,  a  volcano 


20 


BUILDING  STONES  AND  CLAYS 


would  be  formed.  As  shown  in  Fig.  11,  this  would  usually  in- 
volve the  creation  of  the  volcanic  neck  or  passage  through  which 
the  igneous  rock  reached  the  surface,  the  subsequent  building  of  a 
cone  of  ashes  or  lava,  and  in  some  cases  the  flow  of  a  more  or  less 
extensive  lava  sheet  over  the  adjoining  surface. 


Fig.  11.  —  Volcanic  neck  (A),  cone  (B)  and  surface  flow  (C). 

5.  Dykes,  Sheets  and  Sills.  Certain  minor  types  of  occurrence, 
which  may  be  connected  with  either  volcanic  or  intrusive  action, 
remain  to  be  noted.  Igneous  rock  might  reach  upward  toward 
the  surface  through  approximately  vertical  fissures.  The  rock 
which  cooled  in  these  fissures  would  form  a  dyke,  as  illustrated 
in  Figs.  12  and  13.  If  at  any  point  a  supply  of  igneous  rock 
penetrated  laterally  along  the  bedding  planes  of  a  sedimentary 
formation,  it  would  form  on  cooling  an  intrusive  sheet  or  sill. 
Examples  of  these  are  also  shown  in  Figs.  11  and  12. 


A    A    A 


Fig.  12.  — Dykes  (A,  A)  and  sheet  or  sill  (B). 

Texture  of  Igneous  Rocks.  —  When  molten  masses  cooled  in 
large  bodies,  or  at  considerable  depths  below  the  surface,  the 
solidification  was  in  consequence  so  slow  as  to  permit  the  forma- 
tion of  large  crystals  of  the  different  constituent  minerals.  Our 
ordinary  granites  are  good  examples  of  such  slowly  cooled  prod- 


IGNEOUS  ROCKS  IN  GENERAL 


21 


ucts.  But  when  the  local  supply  of  molten  material  was  small, 
or  when  solidification  took  place  at  or  near  the  surface,  the  cool- 
ing was  so  rapid  that  the  resulting  rocks  are  made  up  of  very 
small  mineral  crystals,  often  enveloped  in  a  glassy  matrix;  while 


Fig.  13.  —  Dykes  made  prominent  by  weathering.     (Hayden  Survey.) 

a  still  more  rapid  cooling  might  result  in  a  rock  having  an  entirely 
glassy  structure,  absolutely  free  from  crystals.  If,  as  happened 
in  places,  the  igneous  material  was  introduced  into  the  air  or 
into  water  while  still  molten  (as  in  volcanic  action),  the  result 
was  the  formation  of  porous  products  —  volcanic  ash,  pumice,  etc. 
Perhaps  the  conditions  above  outlined  may  be  more  clearly 
realized  if  they  are  compared  with  a  parallel  series  of  perfectly 


BUILDING  STONES  AND  CLAYS 

familiar  phenomena  which  occur  every  day  in  the  handling  of 
slag  at  blast  furnaces.  If  furnace  slag  is  cooled  with  very  great 
slowness,  it  will  develop  crystals  of  various  silicate  minerals. 
On  the  other  hand,  the  slag  as  it  usually  cools  on  a  slag  bank 
has  an  entirely  glassy  texture.  Finally,  if  the  molten  slag  is 
led  into  water,  or  if  a  current  of  steam,  air  or  water  is  injected 
into  the  stream  of  molten  slag,  the  slag  will  cool  or  granulate  so 
suddenly  as  to  assume  a  porous  texture,  exactly  like  a  volcanic 
ash. 

Structure  in  Igneous  Rocks.  —  Since  all  igneous  rocks  are 
formed  by  direct  cooling  from  a  state  of  fusion,  it  is  obvious  that 
none  of  them  can  show  any  true  bedding,  for  that  is  a  charac- 
teristic of  materials  deposited  by  or  in  water.  The  differences 
in  structure  can  not  be  due  to  the  sorting  influence  of  water,  but 
must  be  entirely  due  to  the  varying  conditions  under  which  they 
cooled,  or  to  the  effects  of  later  earth  movements  on  the  cooled 
mass.  Considering  igneous  rocks  in  general,  two  different  types 
of  structure  may  exist. 

1.  In  an  igneous  rock  which  has  solidified  quietly  from  a  fused 
state,  and  which  has  not  been  later  subjected  to  severe  external 
stresses,  the  constituent  mineral  crystals  are  confusedly  arranged, 
showing  no  trace  of  parallel  banding  or  lamination.     Such  rocks 
are  termed  massive  igneous  rocks.     Most  of  the  granites  used 
for  structural  purposes,  and  practically  all  of  the  trap  rock  used 
commercially,  fall  in  this  class. 

2.  If,  however,  rocks  of  this  same  origin  and  composition  had 
been  subjected,  either  during  or  after  their  cooling,  to  external 
pressure,    a  laminated   structure  might   have   been   developed. 
When  this  has  occurred  under  favorable  conditions   the   con- 
stituent minerals  may    be   arranged   in   more   or   less   definite 
alternating  bands;  while  when  the  lamination  is  less  completely 
developed  the  mineral  crystals  will  merely  be  arranged  with  their 
longer  axes  in  the  same  direction.     In  either  case  the  rock  is 
termed  a  gneiss.     Some  of  the  rocks  which  commercially  are  classi- 
fied as  granite,  and  are  used  in  structural  work,  are  in  reality  suffi- 
ciently well  laminated  to  be  properly  called  gneisses. 

Chemical  Composition  of  Igneous  Rocks.  —  The  igneous  rocks 
consist  largely  of  silica  —  from  35  to  80  per  cent  —  with  lesser 
amounts  of  alumina.  According  to  their  class  they  may  also 
contain  more  or  less  iron  oxides,  lime,  magnesia,  potash  and 


IGNEOUS  ROCKS  IN  GENERAL 


23 


soda.  These  are  the  principal  constituents  which  are  present,  in 
varying  amounts,  in  practically  all  of  the  igneous  rocks.  Many 
other  constituents  are  present  in  small  percentages,  but  are  of 
little  general  importance  and  do  not  require  further  notice  here. 
Such  wide  variation  exists  in  the  composition  of  the  different 
types  of  igneous  rocks,  that  few  general  statements  can  be  made 
which  will  apply  to  the  group  as  a  whole.  Analyses  of  these 
various  rock  types  will  be  given  later,  in  the  chapters  dealing 
with  them  separately,  but  in  the  present  place  attention  may  be 
called  to  the  data  presented  in  Table  3.  This  table  includes 
averages,  of  two  long  series  of  analyses  of  igneous  rocks;  and 
the  two  results  may  fairly  be  regarded  as  closely  representative 
of  the  composition  of  the  average  igneous  rock. 

TABLE  3.— AVERAGE  ANALYSES  OF  IGNEOUS  ROCKS. 


Constituent. 

A. 

B. 

Silica  (SiO2) 

Per  cent. 
59  71 

Per  cent. 
58  75 

Alumina  (A12O3)  * 

16  01 

15.76 

Ferric  oxide  (Fe2O3)  

2  63 

5  34 

Ferrous  oxide  (FeO)  

3  52 

2  40 

Lime  (CaO)  

4  90 

4.98 

Magnesia  (MgO)  

4.36 

4  09 

Potash  (K2O)  

2.80 

2.74 

Soda  (Na2O)  

3.55 

3.25 

Water  . 

1  52 

2  23 

*  Including  small  amounts  of  titanic  oxide  (TiOj). 

A.  Average  by  F.  W.  Clarke,  of  830  analyses  of  American  igneous  rocks. 

B.  Average  by  Barker,  of  397  analyses  of  British  igneous  rocks. 

The  terms  acid  and  basic,  as  often  applied  to  igneous  rocks, 
require  some  note.  Acid  rocks  are  those  containing  high  per- 
centages of  silica  and  low  percentages  of  lime,  magnesia,  alkalies 
and  iron  oxide.  Basic  rocks,  on  the  other  hand,  are  high  in  iron, 
magnesia,  etc.,  and  comparatively  low  in  silica.  The  two  classes 
intergrade  with  each  other  and  the  dividing  point  between  the 
acid  and  the  basic  rocks  is  fixed  by  different  writers  at  different 
percentages  of  silica.  Certainly,  acid  rocks  must  in  average  com- 
position contain  more  silica  than  basic  rocks:  but  the  dividing 
line  is  purely  arbitrary.  It  is  both  convenient  and  logical  to  use 
the  average  analyses  presented  in  the  preceding  table  as  a  basis 
for  fixing  this  dividing  point,  and  to  consider  that  any  igneous 


24  BUILDING  STONES  AND  CLAYS 

rock  higher  in  silica  than  the  average  is  an  acid  rock,  while  any 
rock  lower  in  silica  than  the  average  is  a  basic  rock.  In  the 
present  volume,  therefore,  when  it  is  necessary  to  use  these  terms 
precisely,  the  dividing  point  between  the  two  classes  will  be 
considered  to  be  59  per  cent  of  silica.  The  differences  in  chem- 
ical composition  cause  differences  in  physical  characters.  Certain 
acid  rocks  may,  in  average  density,  range  higher  than  exceptional 
basic  rocks:  but  in  general  the  acid  rocks  are  distinctively  lighter 
than  the  basic. 

Mineral  Constituents  of  Igneous  Rocks.  —  The  igneous  rocks 
which  have  crystallized  out  completely  are  composed  of  an  inti- 
mate mechanical  mixture  of  various  silicate  minerals.  Those 
in  which  the  cooling  has  been  too  rapid  to  permit  of  thorough 
crystallization  consist  more  or  less  entirely  of  a  formless  silicate 
glass.  Since  this  latter  class  can  not  be  identified  by  mineral 
composition,  the  paragraphs  which  immediately  follow  must  be 
understood  to  relate  only  to  such  igneous  rocks  as  are  entirely 
or  largely  crystallized. 

The  total  number  of  mineral  species  which  may  occur  in 
igneous  rocks  is  very  large;  but  only  a  few  of  these  species  are 
of  real  importance  in  the  present  connection.  Fortunately  the 
lighter  colored  coarse-grained  rocks  which  furnish  most  of  our 
structural  stone  usually  contain  few  mineral  species  —  commonly 
only  three  or  four  are  present  in  quantity  —  and  these  are  readily 
recognizable.  The  finer  grained  or  partially  glassy  igneous 
rocks,  on  the  other  hand,  can  not  be  properly  classified  without 
the  aid  of  chemical  analysis  or  microscopic  investigations;  but 
the  rocks  of  this  type  are  not  of  high  industrial  importance  for 
structural  purposes. 

The  minerals  which  make  up  the  bulk  of  the  igneous  rocks 
used  for  structural  purposes  represent  five  species  or  groups  of 
species.  These  are  in  order  of  importance: 

(1)  Quartz. 

(2)  The  feldspars. 

(3)  The  micas. 

(4)  The  amphibole-pyroxene  group. 

(5)  Olivine. 

Several  minor  minerals  are  of  sufficient  importance  to  require 
brief  mention,  while  certain  minerals  which  occur  as  secondary 


IGNEOUS  ROCKS  IN  GENERAL  25 

or  alteration  products  may  also  be  noted.     These  will  be  taken 
up  after  describing  the  five  principal  groups  listed  above. 

(1)  Quartz,  which  is  composed  entirely  of  silica  (SiO2),  occurs 
in  the  granites  and  many  other  igneous  rocks.     It  is  also,  it  may 
be  noted,  the  principal  constituent  of  the  sandstones.     In  the 
granites,  quartz  commonly  occurs  as  a  transparent  or  translucent 
mineral,  varying  in  appearance  from  clear,  colorless  and  glasslike 
to  light  grayish  or  light  bluish.     It  shows  no  regular,  smooth 
surfaces  or  fracture  planes;  but  breaks  with  a  rough,  irregular, 
glassy  fracture.      It   can  not  be  scratched  with  a  knife,  being 
hard  enough  to  scratch  window  glass.     The  specific  gravity  of 
pure  quartz  is  close  to  2.65. 

(2)  The  feldspars  are  a  group,  including  a  long  series  of  com- 
plex silicate  minerals.     The  most  prominent  members  of  this 
group  are  orthoclase,  albite,  labradorite,  anorthite,  oligoclase  and 
microdine.     The  distinctions  between  the  various  feldspars  can 
rarely  be  made  out  except  by  chemical  analysis;  but  the  group, 
taken  as  a  whole,  can  be  described  quite  satisfactorily. 

The  feldspars  occurring  in  most  building  stones  are  commonly 
white  to  gray  or  reddish  in  color  —  more  rarely  dark  blue  or 
gray;  on  breaking,  they  fracture  with  a  very  regular  smooth 
polished  cleavage  surface  in  at  least  one  direction,  and  frequently 
they  show  two  such  regular  cleavages. 

Chemically,  the  feldspars  fall  into  two  quite  distinct  subgroups; 
the  orthoclase  or  potash  feldspars  and  the  plagioclase  or  soda-lime 
feldspars.  The  former  group  contains  only  two  mineral  species 
—  orthoclase  and  microdine  —  which  differ  only  in  optical  charac- 
ters. The  plagioclase  group  is  more  complex,  containing  a  long 
series  of  feldspars  ranging  in  composition  from  albite  (a  soda 
feldspar)  at  the  one  extreme  to  anorthite  (a  lime  feldspar)  at  the 
other.  The  intermediate  stages  in  this  series  have  been  given 
distinct  names,  but  may  probably  be  regarded  simply  as  mixtures 
of  albite  and  anorthite  molecules  in  various  proportions. 

In  the  following  table  the  composition  and  specific  gravity  of 
the  various  feldspars  are  recorded.  Orthoclase  is  placed  first, 
after  which  the  various  plagioclase  feldspars  follow  in  the  order 
of  their  decrease  in  silica  content. 

The  orthoclase  and  plagioclase  feldspars  differ  little  in  appear- 
ance, so  that  it  is  difficult  to  distinguish  them  except  under  the 
microscope  or  by  analysis.  This  is  unfortunate,  for  the  distinc- 


26 


BUILDING  STONES  AND  CLAYS 


tion  between  the  two  subgroups  is  often  important,  since  they 
differ  in  geologic  associations  as  well  as  in  composition.  Ortho- 
clase  is  a  common  constituent  of  the  more  acid  igneous  rocks, 
such  as  the  granites  and  syenites;  while  the  common  feldspar  of 
basic  rocks  such  as  trap,  gabbro  and  basalt  is  invariably  a  plagio- 
clase  feldspar. 

TABLE  4.  — COMPOSITION  AND  SPECIFIC   GRAVITY  OF 
THE  FELDSPARS. 


Name. 

Specific 
gravity. 

Formula. 

Silica. 

Alu- 
mina. 

Potash. 

Soda. 

Lime. 

Orthoclase  .  .  . 
Albite 

2.57 
2  62 

K2O,  A12O3,  6  SiO2 
Na2O  A12O3  6SiO2 

64.60 
68  62 

18.50 
19  56 

16.90 

11  82 

Oligoclase  . 

2  64 

63  70 

23  95 

1  20 

8  11 

2  05 

Andesine 

2.65 

Labradorite 

2.69 

52  90 

30  30 

4  50 

12  30 

Bytownite  .  . 
Anorthite  .  .  . 

2.71 
2.75 

'2CaO,Al2b3,'4SiO2 

43.08 

36.82 

20.10 

One  point  which  often  aids  in  the  separation  of  the  two  groups 
may  be  noted.  The  cleavage  faces  of  orthoclase  are  perfectly 
smooth,  while  close  examination  of  the  cleavage  faces  of  a  plagio- 
clase  feldspar  will  often  show  that  they  are  crossed  by  a  series 
of  close-set  parallel  lines.  Color  and  association  also  aid  some- 
what in  the  distinction.  Orthoclase  is  usually  white,  pinkish, 
red  or  very  light  grayish  in  color;  and  is  frequently  associated 
with  quartz.  A  white  plagioclase  feldspar,  in  a  rock  which  also 
contains  considerable  quartz  and  orthoclase,  is  probably  albite. 
On  the  other  hand,  a  bluish  or  dark  gray  plagioclase  feldspar,  in 
a  rock  containing  little  or  no  quartz  or  orthoclase,  is  labradorite 
or  another  of  the  more  basic  plagioclases. 

(3)  The  micas  occur  in  glistening  scales  or  flakes,  usually  white, 
yellowish  dark  brown,  or  black  in  color.  They  include  two 
common  species  —  muscovite  and  biotite  —  and  several  species 
of  less  importance.  Mica,  the  familiar  " isinglass"  of  stove 
doors,  is  readily  scratched  by  a  knife,  and  even  more  readily 
split  into  thin  leaves  or  flakes  along  its  cleavage  planes.  The 
light-colored  micas  can  not  be  mistaken  for  any  other  common 
mineral  in  igneous  rocks.  The  dark  micas,  however,  might  be 
confused  with  hornblende  or  augite,  since  both  show  the  same 
dark-colored  smooth  glistening  surfaces ;  but  the  splitting  proper- 
ties of  the  mica  are  not  shared  by  hornblende  or  augite. 


IGNEOUS  ROCKS  IN   GENERAL 


27 


Though  a  number  of  species  of  mica  are  recognized,  only  two 
are  sufficiently  common  as  rock-forming  minerals  to  require 
consideration  here.  The  two  common  species  are,  as  above 
noted,  muscovite  and  biotite.  Of  these,  muscovite  is  a  light- 
colored  mica,  occurring  frequently  in  granites,  schists  and  the 
more  acid  gneisses;  but  very  rarely  in  the  gabbros,  basalts  and 
similar  basic  rocks.  Biotite,  on  the  other  hand,  occurs  very 
commonly  in  certain  basic  rocks;  and  somewhat  less  frequently 
than  muscovite  in  the  more  acid  types. 

Fairly  representative  analyses  of  specimens  of  these  micas  are 
given  below: 

TABLE  5.  — ANALYSES  OF  MICAS. 


Muscovite. 

Biotite. 

Silica                                                

46.3 

40.0 

Alumina                        .                   

36.8 

17.28 

Ferric  oxide       

4.5 

0.72 

Ferrous  oxide         

4.88 

JMasrnesia 

23  91 

Potash 

9.2 

8.57 

Comparison  of  these  analyses  will  show  that  muscovite  is 
relatively  high  in  alumina,  while  biotite  contains  large  per- 
centages of  magnesia  and  ferrous  oxide.  This  results  in  charac- 
teristic differences  in  weathering,  for  while  muscovite  is  little 
affected  by  atmospheric  action,  the  oxidation  of  the  ferrous  iron 
in  the  biotite  makes  it  assume  a  more  or  less  rusty  appearance 
on  long  exposure.  Muscovite  is  slightly  lower  in  specific  gravity 
-  2.6  to  3.0,  as  compared  with  the  2.8  to  3.2  of  biotite. 

(4)  The  amphibole-pyroxene  group  includes  a  large  number  of 
species,  two  of  which  are  of  common  occurrence  in  igneous  rocks. 
These  are  hornblende  (amphibole)  and  augite  (pyroxene),  which 
are  not  readily  distinguished  from  each  other  in  the  hand  speci- 
men. Both  are  commonly  green  to  almost  black  in  color,  and 
usually  break  with  one  smooth  fracture  surface;  but  are  dis- 
tinguishable from  the  dark  micas,  which  they  often  resemble  in 
appearance,  in  not  being  readily  split  into  thin  leaves  or  plates. 

Though  non-aluminous  amphiboles  and  pyroxenes  occur,  the 
hornblende  and  augite  which  are  the  common  rock-forming 


28  BUILDING  STONES  AND  CLAYS 

varieties  are  essentially  silicates  of  alumina,  lime,  magnesia  and 
iron.     The  following  analysis  is  fairly  representative. 

Silica 48.8 

Alumina 7.5 

Ferrous  oxide 18.2 

Lime 10.2 

Magnesia 13.6 

Hornblende  occurs  more  frequently  in  diorites  and  granites, 
while  augite  is  characteristic  of  the  more  basic  rocks.  Slight 
differences  of  specific  gravity  are  to  be  noted,  that  of  hornblende 
ranging  commonly  from  3.15  to  3.33,  while  that  of  augite  varies 
from  3.3  to  3.55. 

(5)  Olivine  or  peridot  is  a  silicate  of  iron  and  magnesia  occurring 
as  an  essential  constituent  of  the  ultra-basic  igneous  rocks;  and 
as  a  common  constituent  of  all  the  basic  rocks.  It  usually  occurs 
in  small  glassy  grains,  varying  in  color  from  yellowish  green  to 
olive  green.  The  grains  are  brittle,  and  usually  will  show  one 
smooth  cleavage  or  fracture  surface. 

One  of  the  more  important  relations  of  olivine  to  the  stone 
industry  arises  from  the  fact  that  some  of  the  serpentines  dis- 
cussed in  Chapter  V  have  originated  through  the  alteration  of 
rocks  rich  in  olivine. 

Certain  other  minerals  are  apt  to  be  developed  as  secondary 
products,  in  case  the  rock  has  undergone  alteration  or  more 
or  less  complete  decomposition.  The  more  important  of  these 
secondary  minerals  are  calcite,  magnesite,  kaolinite,  chlorite  and 
serpentine.  It  is  to  be  noted  that,  of  this  group,  kaolinite  is  the 
only  species  likely  to  result  from  the  alteration  of  the  acid  igneous 
rocks;  the  other  four  secondary  minerals  being  more  commonly 
associated  with  the  decomposition  of  basic  rocks. 

The  Classification  of  Igneous  Rocks.  —  The  classification  of 
the  massive  igneous  rocks,  as  at  present  practiced  by  professional 
petrographers,  has  attained  a  degree  of  precision  and  refinement 
which  renders  it  entirely  useless  to  the  engineer  or  quarryman. 
The  systematic  classification  now  adopted  by  most  American 
petrographers  is  based  upon  chemical  analyses  of  a  grade  un- 
attainable in  ordinary  laboratory  practice,  interpreted  and  sup- 
plemented by  means  of  the  microscope.  In  the  hands  of  a 
specialist  such  chemical  and  optical  data  can  be  combined  to 


IGNEOUS   ROCKS   IN   GENERAL  29 

give  results  of  great  exactness,  but  by  others  than  specialists 
they  can  not  be  safely  applied,  and  the  classification  *  based  upon 
them  is  of  no  economic  importance. 

For  our  present  purposes,  the  following  grouping  will  be  found 
sufficiently  accurate  and  precise. 

A.  Rocks  which  are  entirely  crystallized,  so  that  each  of  the 
constituent  minerals  is  recognizable. 

1.  Granites:  composed  essentially  of  quartz  and  feldspar; 

with  usually  lesser  amounts  of  mica,  or  hornblende,  or 
both.  The  feldspar  is  occasionally  all  orthoclase;  but 
commonly  some  plagioclase  is  also  present.  The  mica 
may  be  either  muscovite,  or  biotite,  or  both. 

2.  Syenites:   composed  essentially  of  feldspar,  with  sub- 

ordinate amounts  of  mica  or  hornblende.  Quartz  is 
entirely  or  practically  lacking.  The  feldspar  is  usually 
a  mixture  of  orthoclase  and  plagioclase. 

3.  Diorites:  composed  essentially  of  hornblende  and  felds- 

par, the  former  being  in  excess.  Mica,  usually  biotite, 
may  be  present  in  considerable  quantity.  Quartz  is 
rare  or  absent.  The  feldspar  is  commonly  a  plagio- 
clase, though  orthoclase  may  also  be  present  in  sub- 
ordinate amounts. 

4.  Gabbros:  composed  essentially  of  pyroxene  and  feldspar, 

the  former  being  in  excess.  Olivine  may  be  present, 
as  well  as  biotite.  The  feldspar  is  usually  one  of  the 
more  basic  plagioclases. 

5.  Hornblendites :  composed  essentially  of  hornblende,  felds- 

par being  absent.  Pyroxene  and  olivine  may  be  pres- 
ent in  subordinate  amounts. 

6.  Pyroxenites:  composed  essentially  of  pyroxene,  feldspar 

being  absent.  Hornblende  and  olivine  may  be  present 
in  subordinate  amounts. 

*  The  reader  desirous  of  further  enlightenment  regarding  this  classification 
may,  at  his  own  risk,  read  the  papers  noted  below: 

Cross,  W.,  and  others.  A  quantitative  chemico-mineralogfcal  classifica- 
tion and  nomenclature  of  igneous  rocks.  Journal  of  Geology,  vol.  X.,  pp. 
555-690,  1902. 

Washington,  H.  S.  Chemical  analyses  of  igneous  rocks  published  from 
1884  to  1900,  with  a  critical  discussion  of  the  character  and  use  of  analyses. 
Professional  Paper,  No.  14,  U.  S.  Geol.  Survey,  495  pp.,  1903. 


30  BUILDING  STONES  AND  CLAYS 

7.  Peridotites:  composed  essentially  of  olivine  (peridot), 
feldspar  being  absent.  Pyroxene  and  hornblende  may 
be  present  in  subordinate  amounts. 

B.  Rocks  in  which  the  bulk  of  the  rock  forms  a  dense  fine- 
grained, unrecognizable  groundmass,  through  which  a  few  rela- 
tively large  mineral  crystals  are  scattered.      These  rocks   are 
the  porphyries.     They  may  be  further  subdivided  into  quartz- 
porphyry,  feldspar-porphyry,  etc.,  according  to  the  particular 
mineral  which  makes  up  the  visible  crystals. 

C.  Rocks  in  which  no  mineral  constituents  are  recognizable, 
the  rock  being  a  dense,  fine-grained  mass  of  microscopic  crystals 
often  with  minor  amounts  of  glassy  matter.     Subdivided  on  the 
basis  of  color  and  composition  into :  — 

1.  Felsites;  light  colored,  acid  rocks. 

2.  Basalts;  dark  colored,  basic  rocks. 

D.  Rocks  which  show  no  trace  of  crystallization,  being  glassy 
throughout.     The   volcanic   glasses,    which   require   no   further 
consideration  here. 

Since  any  of  the  above  types  of  igneous  rock  may  have  been 
subjected,  during  or  after  cooling,  to  pressure  sufficient  to  cause 
banding,  we  may  find  types  of  gneisses  corresponding  in  com- 
position to  any  of  the  groups  of  massive  rocks.  A  rock  consisting 
of  quartz,  feldspar  and  mica,  arrayed  in  quite  definite  layers, 
would  be  a  granite-gneiss;  a  similarly  laminated  rock  consisting 
chiefly  of  pyroxene  and  feldspar  would  be  a  gabbro-gneiss;  and 
so  on. 

Commercial  Classification  of  Igneous  Rocks.  —  The  scientific 
classification  of  the  various  igneous  rocks  is  a  matter  of  great 
complexity,  as  has  been  noted  above.  Fortunately  or  unfortu- 
nately, engineers  and  quarrymen  have  adopted  a  very  simple 
working  classification,  recognizing  only  the  following  groups: 

(1)  Granites:  including  the  lighter  colored,  less  dense,  coarser 
grained  igneous  rocks,  usually  containing  much  quartz. 

(2)  Traps:  including  the  dark  colored,  dense,  heavy  igneous 
rocks,  composed  mostly  of  pyroxene,  basic  feldspars,  etc.,  with 
little  or  no  quartz. 

To  these  should  be  added  a  third  class,  usually  derived  from 
basic  igneous  rocks  by  weathering  and  other  alteration  processes. 


IGNEOUS  ROCKS  IN  GENERAL  31 

(3)  Serpentines:  including  a  series  of  (usually  green)  soft 
rocks,  composed  mostly  of  hydrated  magnesium  silicates. 

Pumice,  lava,  and  other  igneous  products  which  have  cooled 
rapidly  at  the  earth's  surface  require  no  special  comment  here, 
being  usually  unfit  for  structural  purposes  and  therefore  of  little 
importance  to  the  engineer.  It  may  be  noted,  however,  that  the 
natural  puzzolan  materials  often  used  as  cements  (pozzuolana, 
trass,  santorin,  etc.)  are  all  volcanic  ashes. 

The  distinction  thus  made  by  the  trade  between  "granite" 
and  "  trap/'  though  not  in  complete  accord  with  scientific  group- 
ing, has  certain  underlying  principles  of  commercial  usefulness. 
The  dark-colored  basic  rocks  called  "traps"  agree  in  being 
tough  and  difficult  to  quarry  and  dress,  of  dark  and  somber 
colors,  and  rather  susceptible  to  weathering;  while  the  light- 
colored  acid  "granites"  are  more  readily  excavated  and  cut, 
usually  of  light  and  pleasing  colors,  and  more  resistant  to  atmos- 
pheric agencies.  The  serpentines  differ  from  both  of  these 
classes  in  their  fairly  uniform  greenish  colors  and  in  their  softness. 

The  relation  between  the  scientific  and  the  commercial  classi- 
fications of  rocks  is  about  as  follows  (compare  page  29,  et.  seq.). 
Under  the  head  of  granite  the  quarry  man  includes  all  the  true 
granites  and  syenites,  aficKhe^  coarser-grained  varieties  of  diorite 
and-gabbro,  though  the  last  of  these  is  rarely  used  for  structural 
purposes.  The  trade  name  trap,  on  the  other  hand,  includes 
the  basalts,  the  peridotites,  pyroxenites  and  hornblendites,  and 
tha4mer-grained  varieties  of  diorite  and  gabbro,  though  most^  . ^. 
commercial  trap  is  -either  basalt  or  a  fine-grained  gabbro.  ^""TPhe 
other/ rocks  listed  in  the  scientific  grouping  —  felsite,  porphyry 
and/ the  volcanic  glasses  —  are  rarely  used  in  structural  work. 
The  serpentines,  though  usually  derived  from  igneous  rocks, 
find  no  place  in  the  scientific  classification  above  presented  be- 
cause they  are  not  original  but  secondary  products. 


,  CHAPTER  III. 
GRANITES  AND  OTHER  ACID  ROCKS. 

Scope  of  the  Term  Granite.  —  The  term  granite,  as  used  in 
the  stone  industry,  and  as  it  will  be  employed  usually  in  the 
present  chapter,  includes  practically  all  of  the  igneous  rocks 
except  the  traps  and  serpentines.  This  is  a  negative  and  appar- 
ently very  loose  definition,  but  as  a  matter  of  fact  the  term  can 
be  defined  much  more  closely  without  seriously  interfering  with 
its  trade  application. 

|j  By  far  the  majority  of  the  " granites"  known  to  the  stone 
trade  are  light-colored,  coarse-grained  stones,  composed  largely 
of  quartz  and  feldspar,  with  usually  some  mica,  occasionally 
hornblende  a»cH-are}y-~ftttgite:  (|  The  commercial  granite,  there- 
fore, is  almost  always  a  rock  of  the  type  which  the  geologist 
would  also  include  in  his  more  restricted  use  of  the  term  granite. 
Occasionally,  however,  we  find  syenites  and  the  coarser-grained 
gabbros  and  diorites  handled  under  the  trade  name  of  "  granite," 
but  though  these  exceptions  require  note,  it  must  be  borne  in 
mind  that  they  are  exceptions.  In  99  cases  out  of  100,  the 
granite  of  the  stone  trade  is  also  the  granite  of  the  geologist. 

In  certain  parts  of  the  country,  however,  the  term  granite  is 
misapplied  to  kinds  of  rock  which  have  no  possible  claim  to  it. 
This  is  often  the  case  in  districts  where  igneous  rocks  are  scarce 
or  entirely  wanting;  and  in  such  districts  sandstone  and  even 
limestone  may  be  found,  in  certain  local  markets,  under  the 
local  trade  name  "granite."  Such  a  misapplication  of  the  term 
has  nothing  to  excuse  it,  from  any  point  of  view,  and  the  most 
reasonable  way  to  treat  it  is  as  an  attempt  to  cheat  the  pur- 
chaser. 

The  trade  distinctions  between  the  different  kinds  of  granites 
are  based  largely  upon  differences  in  color,  coarseness  of  grain 
and  mineral  constituents;  for  most  of  the  technical  properties  and 
commercial  values  of  granites  depend  on  these  three  factors. 

32 


GRANITES  AND  OTHER  ACID   ROCKS  33 

ORIGIN  AND   MODE  OF   OCCURRENCE. 

Origin  of  Granites.  —  All  of  the  rocks  here  grouped  as  granites 
are  of  course  igneous  in  origin.  More  particularly,  their  general 
coarseness  of  crystallization  and  entire  lack  of  any  uncrystalline 
or  glassy  groundmass  indicates  that  they  did  not  reach  the  sur- 
face of  the  earth  at  the  time  when  they  cooled  and  solidified 
from  their  original  state  of  fusion.  If  they  had  so  emerged,  they 
would  have  been  subjected  to  very  rapid  cooling;  and  experience 
with  slags  shows  that  fused  rock  which  cools  quickly  will  take 
the  form  either  of  porous  lava-like  products  or  of  dense  close- 
grained  (or  glassy)  masses.  If,  then,  the  granites  had  reached 
the  earth's  surface  while  still  fused,  the  resultant  quickness  of 
cooling  would  not  have  permitted  the  component  minerals  to 
crystallize  out  completely  in  relatively  large  grains. 

It  is  therefore  fair  to  assume  that  such  coarse-grained  rocks 
as  the  granites  cooled  while  still  some  distance  below  the  earth's 
surface;  being  protected  or  blanketed  from  rapid  cooling  by 
overlying  beds  of  other  rocks.  It  is  true  that  in  many  areas 
granites  now  appear  at  the  surface,  but  this  is  due  to  the  fact 
that  since  their  cooling  and  solidification  the  rock  which  then 
overlay  them  has  been  worn  away  and  carried  off,  mostly  by  the 
action  of  surface  waters. 

Mode  of  Occurrence.  —  The  chief  commercial  granites  are 
found  as  portions  of  large  igneous  masses,  which  at  the  time  of 
cooling  were  injected  or  intruded  into  other  rocks.  Through 
the  processes  of  erosion,  these  igneous  masses  now  appear  at  the 
earth's  surface;  and  in  many  instances  not  only  the  covering 
rock  but  the  rock  which  once  surrounded  them  laterally  has  been 
removed.  In  these  cases,  the  granite  masses  often  project  above 
the  level  of  the  surrounding  country  as  a  boss  or  dome-shaped 
hill. 

Many  of  the  gneissoid  granites  which  are  quarried  at  various 
points  in  the  eastern  portion  of  the  United  States  are  taken  from 
the  ancient  stratiform  masses  alluded  to  on  page  18,  as  forming 
the  bulk  of  the  Archaean  rocks. 

MINERAL  CONSTITUTION   OF  GRANITES. 

Chief  Constituent  Minerals.  —  Most  commercial  granites  con- 
sist largely  of  feldspar  and  quartz,  with  commonly  lesser  amounts 


34  BUILDING  STONES  AND  CLAYS 

of  mica  or  hornblende;  and  often  with  small  percentages  of  other 
minerals,  such  as  tourmaline,  garnet,  apatite,  rutile,  etc.  In  a 
few  syenites  which  reach  the  market  —  notably  the  Fourche 
Mountain  granite  of  Arkansas,  —  quartz  is  scarce  or  lacking;  and 
in  this  particular  Arkansas  case  the  feldspar  is  replaced  by  the 
closely  allied  minerals  elceolite  and  nepheline.  Likewise,  in  a 
few  States  rather  basic  rocks  are  quarried  and  sold  under  the 
name  of  granite;  and  in  these  cases  augite  is  often  present,  while 
the  feldspar  is  one  of  the  plagioclases. 

In  most  commercial  granites,  however,  the  predominant  min- 
eral is  feldspar.  At  times  this  is  orthoclase  alone,  but  commonly 
some  plagioclase  feldspar  is  also  present  in  lesser  quantity. 
Next  to  the  feldspar  in  abundance  is  quartz.  Mica  —  either 
muscovite  or  biotite,  and  frequently  both  —  is  the  third  most 
common  constituent;  while  hornblende  occurs  less  frequently. 

Identification  of  Constituents.  —  When  the  minerals  in  a 
granite  are  in  grains  or  crystals  sufficiently  large  to  be  clearly 
distinguished,  the  different  essential  minerals  can  usually  be 
identified  by  use  of  the  following  key;  which  simply  embodies  in 
comparative  form  certain  facts  noted  on  previous  pages  (see 
pages  25-28). 

A.  Showing  at  least  one  smooth  cleavage  surface. 

I.    Separable  into  thin  leaves;  readily  scratched  by  knife. 
a.    Color  white,  often  stained  yellow.     Mica  (Mus- 
covite) . 

6.    Color  black  or  brown.     Mica  (Biotite). 
II.    Not  separable  into  thin  leaves. 

a.   Color  light  —  usually  whitish,  gray,  pink  or  light 

green.     Feldspar. 

6.    Color  dark  green  to  greenish  black.     Hornblende 
or  Augite. 

B.  No  smooth  surface  apparent;  fracture  rough  and  glassy; 
not  scratched  by  knife;  color  usually  light  gray  to  light  blue, 
translucent.     Quartz. 

Relative  Proportions  of  Minerals.  —  Considerable  industrial  as 
well  as  scientific  interest  attaches  to  a  study  of  the  relative  pro- 
portions in  which  the  various  constituent  minerals  occur  in  any 
given  granite.  There  are  three  ways  of  determining  this.  As 
the  three  methods  differ  in  ease  and  in  accuracy  they  will  be 
briefly  discussed.  They  are: 


GRANITES  AND  OTHER  ACID  ROCKS  35 

1.  Direct  Weighing.  —  In  this  method  the  sample  is  coarsely 
crushed;   the   different   constituent  minerals   are   separated   by 
means  of  heavy  solutions;  and  the  respective  proportions  are 
determined  by  actual  weight.     This  is  the  most  exact  and  most 
tedious  of  the  methods. 

2.  Chemical  Deduction.  —  In   this  method  the  mineral    com- 
position is  calculated  from  the  chemical  analysis  of  the  sample. 
The  analysis  must  be  of  high  grade;  and  errors  are  necessarily 
introduced  because  of  certain  assumptions  which  must  be  made 
as  to  the  composition  of  the  standard  minerals.     This  method 
is  the  second  in  rank,  so  far  as  difficulty  is  concerned;  and  under 
ordinary  conditions  probably  gives  the  least  accurate  results  of 
the  three. 

3.  Surface  Measurement.  —  In  this  method  the  surface  areas 
of  the  various  minerals,  as  exposed  either  on  a  microscope  slide 
or  on  a  polished  surface,  are  measured;  and  the  relative  pro- 
portions of  the  various  constituents  are  calculated  from  these, 
surface  measurements.     This  is  the  easiest  of  the  methods,  and 
ranks  second  in  accuracy. 

Color  of  Granites.  —  Most  granites  of  commercial  importance 
are  light  to  dark  gray,  or  reddish  in  color,  though  occasionally 
granites  of  other  colors  are  marketed.  Granites  ^with  bluish 
tints,  usually  faint,  are,  for  example,  seen  in  certain  areas,  and 
a  few  distinctly  greenish  granites  are  on  the  market.  One 
granite,  used  in  part  for  an  important  structure,  is  quite  distinctly 
yellowish  in  tint.  But  these  exceptions  only  serve  to  emphasize 
the  fact  that  by  far  the  majority  of  granites  used  in  any  large 
way  are  either  gray  or  red. 

When  the  dark  minerals  biotite,  hornblende  and  augite  are  not 
present  in  great  quantity,  the  color  of  a  granite  is  determined 
largely  by  the  color  of  the  feldspar  which  it  contains. 

There  is  some  slight  reason  for  preferring  gray  or  light  red 
granites  to  others,  on  the  ground  of  durability,  for  they  are 
generally  composed  of  minerals  which  are  more  resistant  to 
weathering.  While  granites  should  be  carefully  examined  to 
see  that  the  feldspar  is  fresh  and  translucent,  for  a  chalky  effect 
is  often  produced  by  incipient  decay  of  that  mineral.  Good 
yellow  granites  are  extremely  rare,  for  that  tint  is  usually  due 
to  the  formation  of  rust  through  decay  of  mica  (biotite)  or  some 
other  iron-bearing  minerals.  Black  or  greenish  granites  are  apt; 


36 


BUILDING  STONES  AND  CLAYS 


to  contain  large  percentages  of  minerals  that  are  relatively  non- 
resistant  to  weathering  —  such  as  bkrtite,  mica,  hornblende, 
augite,  the  more  basic  feldspars,  etc. 

TABLE  6.— MINERAL  COMPOSITION  OF  AMERICAN 

GRANITES.     (T.  N.  Dale.) 


State. 

Locality. 

Quartz. 

Ortho        Plagio- 
clase.           clase. 

Micas. 

Horn- 
blende. 

Maine  
Massachusetts  .... 

Jonesport 

Milford 
Quincy 

44.65 

35.66 
30.60 
8.43 

28.85    22.45 

55.91 
60.02 
69.51 

4.05 
8.43 

9.37 

22.06 

.... 

33.50 
33.74 
23  01 

56.00 
58.79 
67.37 



10.50 

7.47 
9.62 

.... 

Rockport 

33.10 
35.82 
31.95 
38  90 

55.80 
57.97 
58.45 
55  50 



11.10 
6.20 
9.60 
5.60 

New  Hampshire  .  . 
Vermont 

Becket 

Milford 
u 

n 

u 

Conway 
Redstone 

u 

Madison 
Hardwick 

33.88 
34.70 
49.35 

27.09 
36.76 
27.40 
17,.  10 
31.04 
28.65 
38.26 
28.60 

21.75 

58.86 
59.60 
28.55     15.37 

29.72    34.03 
27.58    29.16 
29.28    27.70 
31.30    45.22 
63.15 
65.30 
54.79 
67.20 

62.05 

'e'.57 

8.58 
6.50 
13.51 
5.74 
5.81 
5.55 
6.95 
4.20 

16.20 

7.26 
5.70 

Newark 

30.30 

64.80 

4.64 

Randolph 
Barre 
Woodbury 

21.20 
26.58 
29.15 

76.50 
65.52 
64.35 

2.30 
7.90 
6.48 



(i 

31.22 
27.10 

63.11 
65.60 

5.67 
7.30 

Rhode  Island  
tt 

Rochester 
Westerly 

29.60 

36.09 
25.28 

62.10 

28.44    30.63 
20.29    44.48 

8.30 

4.09 
7.43 

ti 

n 

29.87 

35.40    28.35 

6.74 

In  many  cases,  however,  the  selection  of  stone  for  a  structure 
rests  with  the  architect,  not  with  the  engineer,  and  this  occa- 
sionally brings  about  surprising  results.  In  one  instance  which 
came  to  attention  an  architect  of  repute  paid  special  prices  to 
obtain  what  seemed  to  him  a  particularly  desirable  grade  of 


GRANITES  AND  OTHER  ACID  ROCKS  37 

•*•  <  '.•'£.*_ 

stone.  He  had  selected  this  variety  because  of  its  soft  yellowish 
tint,  and  apparently  did  not  realize  that  it  was  simply  the  weath- 
ered phase  of  a  bluish  granite,  and  owed  its  soft  colors  to  a  pretty 
thorough  decay  of  its  feldspar.  Such  a  case  is  of  course  excep- 
tional, but  the  desire  for  a  satisfactory  color  effect  should  never 
be  allowed  to  conflict  with  the  necessity  for  obtaining  a  sound 
stone. 


STRUCTURE  AND   TEXTURE   OF   GRANITES. 

Granites  are  made  up  of  closely  interlocking  crystals  of  various 
minerals.  These  crystals  may  differ  greatly  in  size;  they  may 
show  fairly  definite  banding  or  may  be  entirely  without  any 
orderly  arrangement.  The  granite,  considered  as  a  rock  mass, 
may  present  certain  phenomena  as  to  obvious  or  incipient  frac- 
ture planes.  All  of  these  features  require  consideration  under 
the  present  heading. 

Coarseness  of  Crystallization.  —  Granites  vary  widely  in 
coarseness  of  crystallization,  from  fine-grained  rocks  in  which 
the  individual  crystals  of  quartz  and  feldspar  may  be  one- 
fiftieth  of  an  inch  or  even  less  in  average  diameter,  up  to  coarse 
aggregates  in  which  the  quartz  and  feldspar  may  average  an 
inch  or  more  in  diameter. 

The  size  of  grain  has  an  important  bearing  on  the  value  of  the 
stone  for  various  uses.  This  effect  may  be  briefly  summarized 
as  follows: 

1.  For  monumental  work,  or  where  a  high  polish  is  desirable, 
the  finest-grained  stone  is  most  suitable. 

2.  For  structural  work,  the  medium-grained  stones  are  best 
adapted. 

3.  Coarse-grained  stone  can  be  used  for  little  except  crushed 
stone. 

4.  Very    coarse-grained    stones  —  the    pegmatites  —  may,    as 
later  noted,    furnish   supplies  of   quartz   and  feldspar   for   the 
pottery  and  other  industries. 

Laminated  or  Gneissoid  Structure.  —  The  term  gneiss  is 
applied  to  rocks  which  have  the  same  chemical  and  mineralogical 
composition  as  the  granites  and  their  allies,  and  which  from  their 
associations  and  occurrence  are  usually  known  to  be  of  igneous 
origin;  but  in  which  the  constituent  minerals  are  arranged  in 
roughly  parallel  layers  or  bands. 


38 


BUILDING  STONES  AND  CLAYS 


In  a  granite,  or  any  other  normal  igneous  rock,  the  various 
mineral  constituents  are  scattered  through  the  rock  without 
showing  any  trace  of  systematic  arrangement;  and  this  lack  of 
arrangement  is  exactly  what  would  be  expected  to  result  when 
a  large  mass  of  fused  rock  cools  down  without  disturbance 
from  external  forces.  In  places,  however,  we  find  rocks  of 
undoubtedly  granitic  composition  and  origin,  but  differing  from 
normal  granites  in  that  they  show  a  more  or  less  laminated  or 


Fig.  14.  —  Lamination  and  joint  planes  in  gneiss.     (Photo  by  E.  C.  Eckel.) 

banded  structure  (Fig.  14).  On  examination,  this  is  seen  to  be 
due  to  the  fact  that  the  constituent  minerals  (quartz,  feldspar, 
mica,  etc.)  of  these  banded  or  gneissoid  granites  are  arranged  in 
roughly  parallel  layers.  Since  these  rocks  are  undoubtedly 
igneous  in  origin,  this  lamination  can  not  have  originated  in  the 
same  way  as  the  beds  and  layers  seen  in  sedimentary  rocks, 
though  the  final  result  is  much  the  same  so  far  as  appearance  goes. 
Some  further  explanation  is  therefore  required  as  to  the  origin 
of  this  gneissoid  structure. 

It  has  been  said  that  the  laminated  appearance  is  due  to  the 


GRANITES  AND  OTHER  ACID  ROCKS  39 

fact  that  the  minerals  are  arranged  in  parallel  layers.  This 
parallelism,  in  its  simplest  form,  is  carried  only  to  the  stage  that 
the  longer  axes  of  the  various  mineral  crystals  are  so  arranged 
as  to  lie  in  the  same  plane.  In  more  extreme  cases,  there  has 
been  also  some  degree  of  segregation  of  the  different  mineral 
constituents,  so  that  a  layer  of  quartz,  practically  free  from  mica 
or  feldspar,  will  lie  next  to  a  layer  of  mica  or  feldspar  containing 
practically  no  quartz. 

All  of  this  rearrangement  of  the  minerals,  whether  it  be  of  the 
simpler  or  of  the  more  complex  type,  must  have  originated 
through  the  action  of  external  stresses  on  the  granite  mass,  either 
during  its  slow  cooling  from  fusion  or  at  a  later  date.  If  the 
latter,  it  is  obvious  that  almost  complete  refusion  of  the  rock 
must  have  occurred,  in  order  that  the  gneissoid  structure  could 
be  produced. 

It  may  be  noted  here  that  few  granites,  even  those  which  show 
absolutely  no  trace  of  lamination  when  viewed  in  the  mass,  have 
escaped  entirely  from  the  effects  of  strain,  either  external  or 
internal,  occurring  during  or  after  their  cooling.  This  is  evi- 
denced by  the  phenomena  of  rift  and  grain,  referred  to  in  later 
paragraphs. 

Sheet  Structure.  —  In  many  regions  it  is  noted  that  granite 
masses  show  a  more  or  less  irregular  division,  or  tendency  to 
division,  into  sheets  roughly  parallel  to  the  exposed  surface  of 
the  mass  (Fig.  15).  This  sheeting  has  been  ascribed  to  the 
effects  of  temperature  changes  on  the  exposed  surfaces;  and  in 
many  cases  this  explanation  is  doubtless  sufficient.  At  times, 
however,  evidence  is  found  that  similar  structures  are  developed 
at  considerable  depths  below  the  surface,  and  the  obvious  in- 
adequacy of  surface  temperatures  as  causes  of  deep  structural 
changes  has  led  various  geologists  to  ascribe  some  or  all  sheeting 
structure  to  strains  induced  during  the  original  cooling  of  the 
mass,  or  to  the  effects  of  later  external  stresses. 

Rift  and  Grain.  —  Granite,  not  being  a  stratified  rock,  of 
course  does  not  possess  the  bedding  planes  which  practically  all 
of  the  stratified  rocks  exhibit,  and  along  which  they  usually 
split  most  readily.  The  laminated  granites  or  gneisses,  it  is 
true,  split  easily  in  the  planes  of  their  lamination  which  thus 
have  the  same  structural  effect  as  the  bedding  planes  of  sedi- 
mentary rocks. 


40 


BUILDING  STONES  AND  CLAYS 


Even  the  most  massive  granites,  however,  such  as  show  no 
trace  of  lamination  or  gneissoid  structure  to  the  eye,  are  found 
by  the  quarryman  and  stone  dresser  to  break  and  cut  more 
readily  in  certain  directions  than  in  others.  There  are  com- 
monly two  such  planes  of  relatively  easy  fracture,  usually  at 
about  right  angles  to  each  other.  The  quarryman  speaks  of  the 
planes  of  easiest  fracture  as  the  rift,  and  of  the  other  plane  as 
the  grain. 


Fig.  15.  —  Sheet  structure  in  granite.     (Photo  by  E.  C.  Eckel.) 


The  fact  that  an  apparently  massive  rock  does  possess  such 
planes  of  relatively  easy  fracture  seems  to  depend  upon  the 
existence  of  minute  microscopic  fractures  crossing  the  rock  in 
the  direction  of  the  planes,  or  in  the  direction  of  one  of  them. 
These  microscopic  fractures,  which  are  practically  incipient 
planes  of  cleavage,  may  in  some  cases  be  due  to  internal  stresses 
set  up  during  the  original  cooling  of  the  granite;  but  in  most 
cases  they  are  probably  due  to  the  effect  of  earth  movement  on 
the  rock  after  its  cooling. 


GRANITES  AND  OTHER  ACID  ROCKS  41 

For  more  detailed  discussion  of  these  phenomena  reference 
may  be  made  to  the  papers  by  Dale  and  others  cited  below.* 

Value  of  Microscopic  Work  on  Granites.  —  The  examination 
of  a  thin  section  of  a  granite  under  the  petrographic  microscope 
should  result  in  identifying  accurately  the  component  minerals 
of  the  stone,  and  in  affording  some  estimate  as  to  their  relative 
abundance.  So  far  the  results  are  of  merely  scientific  interest, 
and  if  microscopic  work  could  produce  no  further  information 
it  might  be  dispensed  with  altogether.  Fortunately,  however, 
it  occasionally  affords  results  which  justify  its  use  in  the  study 
of  a  structural  granite. 

The  data  which  under  favorable  circumstances  may  be  ob- 
tained by  the  aid  of  the  microscope  relate  to  the  physical  con- 
dition of  the  component  minerals,  and  of  the  rock  itself.  In- 
cipient decay  of  the  feldspars,  partial  rusting  of  the  iron-bearing 
minerals  and  the  existence  of  minute  cleavage  planes  in  the  rock 
may  be  noted  by  the  investigator.  All  of  these  data  are  of  a 
class  which  possesses  economic  as  well  as  theoretical  interest. 

CHEMICAL   COMPOSITION  OF   GRANITES. 

Value  of  Chemical  Work  on  Granites.  —  The  strength  of  a 
granite  is  not  directly  related  to  its  chemical  composition,  so 
that  chemical  analysis  is  of  no  practical  importance  in  deter- 
mining the  possible  strength  of  the  stone.  It  will,  however, 
throw  a  little  light  on  its  other  physical  properties  —  for  example, 
the  denser  granites  are  usually  those  lowest  in  silica  —  but  even 
then  it  will  be  found  quicker  and  less  expensive  to  make  specific 
gravity  determinations  directly  rather  than  to  attempt  to  infer 
their  results  from  a  chemical  analysis. 

So  far  as  durability  is  concerned  the  case  for  chemical  work  is 
but  little  stronger,  though  here  also  we  might  draw  some  rather 
hazardous  conclusions,  such,  for  example,  as  that  the  rocks  lowest 
in  silica  will  probably  prove  less  durable  than  rocks  of  more  acid 
type. 

*  Dale,  T.  N.  Rift  and  grain  (in  granites).  Bull.  313,  U.  S.  Geol.  Survey, 
pp.  26-29,  1907.  Also  Bull.  354,  U.  S.  G.  S.,  pp.  19-22.  1908. 

Tarr,  R.  S.  The  phenomena  of  rifting  in  granite.  Amer.  Journal  Science, 
3d  series,  vol.  41,  pp.  267-272.  1891. 

Whittle,  C.  L.  Rifting  and  grain  in  granite.  Engineering  and  Mining 
Journal,  vol.  70,  p.  161,  1900. 


42  BUILDING  STONES  AND  CLAYS 

From  the  purely  engineering  point  of  view,  therefore,  there  is 
but  little  reason  for  making  a  chemical  analysis  of  a  granite.  If 
the  analysis  be  a  really  good  one,  however,  it  will  be  of  service  in 
assigning  the  stone  to  its  proper  place  in  the  geological  classi- 
fication. On  the  other  hand,  analyses  as  made  and  reported 
by  an  ordinary  laboratory  will  be  of  little  use  to  any  one  or  for 
any  purpose. 

Normal  Chemical  Composition  of  Granite.  —  The  term  granite, 
as  used  in  the  stone  trade,  is  construed  so  broadly  that  at  first 
sight  it  might  seem  impossible  to  say  anything  definite  concern- 
ing the  average  or  normal  chemical  composition  of  granite.  This 
has,  at  any  rate,  been  the  attitude  taken  by  most  of  the  writers 
on  this  subject. 

As  a  matter  of  fact,  however,  a  study  of  the  subject  will  soon 
prove  that  the  difficulty  is  more  imaginary  than  real;  and  that 
it  is  due  chiefly  to  a  failure  to  realize  that  the  occurrence  of  a 
few  abnormal  types  does  not  seriously  disturb  the  average  result. 
It  is  probably  safe  to  say  that  there  is  really  not  much  more 
variation  in  the  composition  of  commercial  granite  than  there  is 
in  the  composition  of  a  number  of  samples  of  commercial  Port- 
land cement.  That  is  to  say,  if  we  could  sample  all  of  the  granite 
sold  in  any  given  year,  the  range  in  either  direction  from  the 
average  would  not  be  much  greater  than  in  a  similar  series  of 
cement  samples. 

The  extent  of  this  range  in  granite  composition  is  well  illus- 
trated in  the  series  of  tables  of  granite  analyses  (Tables  8  to 
24).  In  those  tables  it  is  accentuated  because  of  the  inclusion 
of  a  number  of  gneisses,  syenites,  etc.  These  are  marketed  as 
granites,  and  their  analyses  are  presented  for  completeness,  but 
it  must  not  be  forgotten  that  the  total  quantity  of  such  stone 
sold  is  unimportant  in  comparison  with  the  quantity  of  normal 
granite. 

The  following  table  contains  a  number  of  average  analyses. 
The  Georgia  average  is  taken  from  a  report  by  T.  L.  Watson; 
all  of  the  other  averages  were  prepared  by  the  present  writer. 
The  final  average  in  the  last  column  is  merely  the  arithmetical 
average  of  the  preceding  seven  columns  —  a  method  of  treat- 
ment which  is  accurate  enough  for  our  present  purposes. 


GRANITES  AND  OTHER   ACID   ROCKS 


43 


TABLE  7.  — AVERAGE  COMPOSITION  OF  GRANITES. 


State  

Maine. 

Massa- 
chu- 
setts. 

New 
Jersey. 

Vir- 
ginia. 

South 
Caro- 
lina. 

Georgia. 

Wiscon- 
sin. 

Final 
average. 

Number  of  analyses 
averaged. 

!     7 

10 

10 

6 

15 

21 

7 

76 

Silica  
Alumina  

73.02 
14.89 

75.65 
13.30 

73.75 

13.91 

70.79 
14.04 

69.67 
15.24 

69.67 

16.63 

73.72 
13.38 

72.42 
14.48 

Ferric  oxide  

0.83 

1.41 

1.06 

1.90 

1.79 

1.28 

1.60 

1.41 

Ferrous  oxide  

0.86 

0.70 

1.23 

1.32 

2.48 

1.02 

1.09 

Lime  .        

1.02 

0.88 

1.27 

2.03 

1.81 

2.13 

1.62 

1.54 

Magnesia  

0.13 

0.06 

0.41 

0.76 

0.66 

0.55 

0.41 

0.43 

Potash  

5.20 

4.81 

4.51 

4.43 

4.46 

4.71 

3.63 

4.54 

Soda 

3.44 

4.10 

3.43 

3.63 

3.64 

4.73 

3.17 

3.73 

Water           

0.46 

0.34 

0.27 

0.41 

0.45 

0.43 

0.34 

From  the  averages  in  the  above  table  it  will  be  seen  that  all 
the  striking  individual  variations  are  eliminated  as  soon  as  even 
a  small  group  of  analyses  are  averaged.  The  final  average  in 
the  last  column  may  be  accepted  as  a  fair  statement  of  the  normal 
composition  around  which  granites  range. 

Composition  of  American  Granites.  —  The  following  tables  con- 
tain analyses  of  representative  American  granites,  arranged  by 
states. 


TABLE  8.  — ANALYSES  OF  GRANITES:  MAINE. 


• 

2 

3 

4 

5 

6 

7 

Aver- 
age. 

Silica 

73.02 

74.64 

71  54 

73.48 

74  54 

70  94 

72  97 

73  019 

Alumina  

16.22 

14.90 

14.24 

15.26 

13.30 

15.68 

14.63 

14.890 

Ferric  oxide  
Ferrous  oxide  
Lime 

2.59 
0.94 

1.56 
0'39 

0.74 
1.18 
0.98 

1.42 

0.88 

0.92 
0.79 
1  26 

2.29 
1  23 

i!73 
1  48 

0.83 
0.857 
1  023 

Magnesia  
Potash  

tr 
3.42 

tr 

6.88 

0.34 
4.73 

0.09 
5.66 

0.01 
5.01 

0.19 
5  54 

0.27 
5  18 

0.131 

5.203 

Soda 

3  60 

0  41 

3  39 

3  12 

3  69 

3  58 

3  28 

3  439 

Water  

0.61 

0.55 

0.37 

0.33 

0.465 

1.  Blue  Hill,  Hancock  County;  Ricketts  &  Banks,  analyst;  20th  Ann. 

Rep.  U.  S.  G.  S.,  pt.  6,  p.  393. 

2.  Blue  Hill,  Hancock  County;  H.  J.  Williams,  analyst;  20th  Ann.  Rep. 

U.  S.  G.  S.,  pt.  6,  p.  393. 


44 


BUILDING  STONES  AND   CLAYS 


3.  North  Jay,  Franklin  County;  E.  T.  Rogers,  analyst;  20th  Ann.  Rep. 

U.  S.  G.  S.,  pt.  6,  p.  392. 

4.  Waldsboro,   Lincoln  County;  Ricketts  &  Banks,  analyst;  20th  Ann. 

Rep.  U.  S.  G.  S.,  pt.  6,  p.  391. 

5.  High  Isle,  Knox  County;  J.  F.  Kemp,  analyst;  Bull.  313,  U.  S.  G.  S., 

p.  122. 

6.  Hurricane  Island,  Knox  County;  Ricketts  &  Banks,  analyst;  Bull.  313, 

U.  S.  G.  S.,  p.  137. 

7.  Jonesboro,  Washington  County;  Ricketts  &  Banks,  analyst;  Bull.  313, 

U.  S.  G.  S.,  p.  170. 


TABLE  9.  — ANALYSES  OF  GRANITES:  MASSACHUSETTS. 


l 

2 

3 

4 

5 

6 

7 

8 

9 

10 

Aver- 
age. 

Silica  
Alumina  .  . 
Ferric  ox.  . 
Ferrous  ox 

76.07 
12.67 
2.00 

76.95 
11.15 
0.25 
0.55 
tr. 
tr. 
5.03 
5.60 
0.20 

69.46 
17.50 
2.30 

81.05 
14.70 
2.71 

77.08 
12.54 
0.95 

72.07 
14.43 
1.25 
0.89 
1.18 
tr. 
5.41 
5.85 
0.35 

75.77 
13.59 
1.14 
0.52 
0.94 
tr. 
n.d. 
n.d. 
0.49 

76.52 
12.21 

"2".  66 
0.79 
0.13 
4.68 
2.86 
0.41 

73.93 
12.29 
2.91 
1.55 
0.31 
0.04 
4.63 
4.66 
0.41 

77.61 
11.94 
0.55 
0.87 
0.31 
tr. 
4.98 
3.80 
0.23 

75.651 
13.302 
1.406 
0.704 
0.881 
0.064 
4.813 
4.100 
0.335 

Lime 
Magnesia  . 
Potash  .  .  . 
Soda 

0.85 
0.10 
4.71 
3.37 

2.57 
0.31 
4.07 
3.01 
0.82 

1.10 
tr. 
n.d. 
n.d. 
0.44 

0.75 
0.01 
4.99 
3.64 

Water 

1.  Milford,  Worcester  County;  C.  F.  Chandler,  analyst;  20th  Ann.  Rep. 

U.  S.  G.  S.,  pt.  6,  p.  404. 

2.  Milford,  Worcester  County;  H.  P.  Talbott,  analyst;  20th  Ann.  Rep. 

U.  S.  G.  S.,  pt.  6,  p.  403. 

3.  Chester,  Hampden  County;  J.  F.  Kemp,  analyst;  18th  Ann.  Rep.  U.  S. 

G.  S.,  pt.  5,  p.  965. 

4.  Cape  Ann,  Essex  County;  Watertown  Arsenal,  analyst;  20th  Ann.  Rep. 

U.  S.  G.  S.,  pt.  6,  p.  402. 

5.  Milford,  Worcester  County;  L.  P.  Kinnicutt,  analyst;  Min.  Res.  U.  S., 

1903,  pamphlet  ed.,  p.  119. 

6.  Milford,  Worcester  County;  R.  H.  Richards,  analyst;  Min.  Res.  U.  S., 

1903,  pamphlet  ed.,  p.  119. 

7.  Milford,  Worcester  County;  R.  H.  Richards,  analyst;  Min.  Res.  U.  S., 

1903,  pamphlet  ed.,  p.  119. 

8.  Milford,  Worcester  County;  R.  C.  Sweetzer,  analyst;  Bull.  354,  U.  S. 

Geol.  Surv.,  p.  88. 

9.  Quincy,  Mass.;   H.  S.  Washington,  analyst;  Bull.  354,  U.  S.  Geol. 

Surv.,  p.  93. 

10.  Rockport,  Mass.;  H.  S.  Washington,  analyst;  Bull.  354,  U.  S.  Geol. 
Surv.,  p.  123 


GRANITES  AND  OTHER  ACID   ROCKS 


45 


TABLE  10.  — ANALYSES  OF  GRANITES:  NEW  HAMPSHIRE. 


1 

2 

3 

4 

5 

6 

Silica  

73.15 

72.47 

71.44 

70.42 

66.80 

74.47 

Alumina           ) 
Ferric  oxide     ?  

17.04 

16.17 

14.72 
2.39 

14.64 
1.54 

18.29 

14.15 
1.16 

Ferrous  oxide  ; 
Lime  . 

0  81 

0.41 
1.65 

0.46 
tr. 

2.34 
tr. 

5.35 
1.70 

1.21 
1  70 

Magnesia  
Potash 

0.30 
5  74 

0.14 
4  83 

0.96 
0  89 

1.20 
0  71 

i  77 

0.63 
4  14 

Soda 

2  05 

3  43 

7  66 

7  80 

6  09 

1  97 

Water. 

0  26 

1.  Troy,  Cheshire  County;  L.  P.  Kinnicutt,  analyst;  20th  Ann.  Rep.  U.  S. 

Geol.  Surv.,  pt.  6,  p.  418. 

2.  Mason,  Hillsboro  County;  Ricketts  &  Banks,  analysts;  20th  Ann.  Rep. 

U.  S.  Geol.  Surv,,,  pt.  6,  p.  418. 

3.  Redstone,  Carroll  County;  F.  C.  Robinson,  analyst;  20th  Ann.  Rep. 

U.  S.  Geol.  Surv.,  pt.  6,  p.  417. 

4.  Redstone,  Carroll  County;  F.  C.  Robinson,  analyst;  20th  Ann.  Rep. 

U.  S.  Geol.  Surv.,  pt.  6,  p.  417. 

5.  Lancaster,  Coos  County;  E.  R.  Angell,  analyst;  Min.  Res.  U.  S.,  1903, 

pamphlet  ed.,  p.  136. 

6.  Concord;  Sherman  &  Edwards,  analysts;  Bull.  354,  U.  S.  G.  S.,  p.  150. 


TABLE  11.  — ANALYSES  OF  GRANITES:   CONNECTICUT. 


• 

2 

3 

4 

Silica  (SiO2) 

68  40 

72  73 

72  06 

68  11 

Alumina  (AlgOs) 

15  75  ) 

14  83 

14  28 

Ferric  oxide  (Fe2Os) 

2  97  £ 

16  95 

1  28  ) 

Ferrous  oxide  (FeO)  .   . 

0  65  ) 

0  64  f 

2.63 

Lime  (CaO)  ... 

1  64 

1  05 

1  20 

1  86 

Magnesia  (MgO)  
Potash  (K2O)  

0.12 
5  78 

tr. 
8  15 

0.13 
5  64 

0.68 
5  46 

Soda  (Na2O)  

4.16 

0  90 

4  31 

6  57 

Water  above  100°  C.  ) 

0  48 

0  22 

0  65 

n  d 

Water  below  100°  C.  }  ' 

1.  Millstone  Point,  H.  T.  Vulte,  analyst. 

2.  Red  granite  Co.,  quarry,  Stony  Creek, 

L.  P.  Kinnicutt,  analyst. 

3.  Brooklyn  Quarry,  Stony  Creek, 

H.  T.  Vulte,  analyst. 

4.  Booth   Bros,  quarry,   Waterford;   Ricketts   &   Banks,  analysts;  20th 

Ann.  Rep.  U.  S.  G.  S.,  pt.  6.,  p.  364. 


Bulletin  Geol.  Soc.  America, 
vol.  10,  p.  375. 


46 


BUILDING  STONES  AND  CLAYS 


TABLE   12.  — ANALYSES  OF  GRANITES:  VERMONT. 


i 

2 

3 

Silica                   

69.56 

77.52 

69.89 

Alumina       

15.38 

16.78 

15.08 

Ferric  oxide 

2  65 

0  84 

1  04 

Ferrous  oxide 

1.46 

Lime                                 

1.76 

2.56 

2  07 

Magnesia            .       

tr. 

0.32 

0.66 

Potash   

4.31 

0.62 

4.29 

Soda      

5.38 

1.21 

4.73 

Water 

1.02 

0.33 

0  54 

1.  Barre,  Washington  County;  W.  C.  Day,  20th  Ann.  Rep.  U.  S.  Geol. 

Surv.,  pt.  6,  p.  445. 

2.  Bethel,  Windsor  County;  C.  S.  McKenna;  Min.  Res.  U.  S.,  1903,  p.  177. 

3.  Barre,  G.  I.  Finlay,  Rept.  Vt.  State  Geol.  for  1902,  p.  55. 


TABLE  13.  — ANALYSES  OF  GRANITES:  RHODE  ISLAND. 


i 

2 

3 

Silica  (SiO»)  .                

71.23 

71.64 

73.05 

Alumina  (AJ2O3) 

13.65 

15.66 

14.53 

Titanic  oxide  (FejOs) 

0.21 

Ferric  oxide  (F^Og) 

1.70  ) 

Ferrous  oxide  (FeO)                   .      .  . 

1.00  J 

2.34 

2.96 

Manganous  oxide  (MnO)  

0.05 

tr. 

tr. 

Lime  (CaO)        

2.31 

2.70 

2.06 

Magnesia  (MgO)     

0.75 

tr. 

tr. 

Potash  (K2O)           

3.79 

5.60 

5.39 

Soda  (Na2O) 

3.55 

1  58 

1.72 

Water  above  100°  C.  ) 
Water  below  100°  C.  ('  ' 

1.72 

0.48 

0.29 

1 .  Conanicut  Island,  L.  V.  Pirsson,  analyst. 


Bulletin  Geol.  Soc.  America, 


GRANITES  AND  OTHER  ACID  ROCKS 


47 


TABLE   14.  — ANALYSES    OF    GRANITES:    NEW    YORK,     PENN- 
SYLVANIA,  AND   DELAWARE. 


Constituent. 

1 

2 

3 

4 

5 

Silica  
Alumina             

63.19 
10.50 

66.72 
16.15 

69.10 
14.69 

74.84 
18.90 

67.98 
15.14 

Ferric  oxide  

10.97  ) 

j    4.63 

3.69  1 

Ferrous  oxide   

1.51  [ 

.42 

)     n.d. 

\ 

.oy 

Lime 

6.12 

2.30 

1.90 

1.54 

5.89 

IVIagnesia 

1.44 

0.73 

0.68 

0.92 

0.53 

Potash 

4.02 

5.66  ) 

(    0.45 

9.00 

Soda                             .  .    . 

1  .92 

4.36  ( 

(    4.32 

Water                          

0.19 

0.77 

0.30 

1.  Hornblende  diorite.     lona  Island,  N.  Y.     J.  F.  Geiste,  analyst.     20th 

Ann.  Rep.  U.  S.  Geol.  Sur.,  pt.  6,  p.  421. 

2.  Augite  syenite.     Little  Falls,  Herkimer  County,  N.  Y.     E.  W.  Morley, 

analyst. 

3.  Hadley,    Saratoga    County,    N.  Y.      Pittsburg    Testing    Laboratory, 

analyst.     Min.  Res.  U.  S.  for  1903. 

4.  Ridley  Park,  Chester  County,  Pa.     Solvay  Company,  analyst.     Min. 

Res.  U.  S.  for  1903. 

5.  Augustine,   Newcastle  County,   Delaware.     Booth,   Garrett   &  Blair, 

analyst.     Min.  Res.  U.  S.  for  1903. 


TABLE   15.— ANALYSES  OF  GRANITES:   NEW  JERSEY. 


1 

2 

3 

4 

5 

6 

7 

8 

9 

10 

Aver- 
age. 

Silica  (SiO2)  . 

71.91 

77.59 

74.36 

75.56 

69.48 

75.02 

75.15 

74.70 

68.60 

75.17 

73.754 

Alumina 

(M20Z\.  .  .  . 

15.71 

10.53 

12.75 

12.61 

16.42 

13.73 

14.65 

15.45 

14.72 

12.55 

13.912 

Ferric  oxide 

(Fe2O3)   ... 

0.21 

0.21 

2.09 

0.64 

0.56 

0.83 

0.11 

0.08 

4.29 

1.54 

1.056 

Ferrous  oxide 

(FeO)  

0.13 

1.74 

1.35 

1.16 

2.60 

0.99 

0.90 

0.64 

1.41 

1.41 

1.233 

Lime  (CaO)  . 

0.70 

0.76 

0.82 

0.84 

3.45 

0.88 

0.92 

1.70 

1.46 

1.15 

1.268 

Magnesia 

(MgO)  

0.03 

1.01 

0.11 

0.05 

1.15 

0.03 

0.04 

0.06 

0.38 

0.21 

0.407 

Potash  (K2O) 

8.60 

5.30 

3.76 

5.93 

1.18 

4.74 

4.71 

2.62 

3.52 

4.62 

4.506 

Soda  (Na2O)  . 

2.61 

1.58 

3.44 

2.35 

4.59 

3.36 

3.60 

4.90 

4.82 

3.07 

3.432 

Water  (H2O). 

0.27 

0.60 

0.20 

0.42 

0.34 

0.17 

0.24 

0.10 

0.16 

0.22 

0.272 

Analyses  1-10  by  R.  B.  Gage.     Quoted  from  An.  Rep.  State  Geologist, 
N.  J.,  for  1908. 

1.  Coarse  grained  pink  granite,  Pompton  Junction. 

2.  Gneiss  inclusions  in  preceding  granite. 

3.  Gray  gneissoid  granite,  di  Laura's  quarry,  near  Haskell. 

4.  Pinkish  granite-gneiss,  Charlotteburgh. 


48 


BUILDING  STONES  AND  CLAYS 


5.  Dark  gray  granite,  Malley's  quarry,  Morris  Plains. 

6.  Reddish  granite-gneiss,  Allen  quarry,  Waterloo. 

7.  Whitish  granite-gneiss,  quarry  two  miles  north  of  Waterloo. 

8.  White  granite-gneiss,  D.  L.  &  W.  R.  R.  quarry  south  of  Cranberry  Lake. 

9.  Gray  granite,  Kice's  quarry,  north  of  German  Valley. 
10.  Light  gray  gneiss,  Kice's  quarry,  west  of  German  Valley. 

TABLE  16.  — ANALYSES  OF  GRANITES:  MARYLAND. 


1 

2 

3 

4 

5 

6 

7 

Silica  

74.87 

72.57 

71.79 

71.45 

70.45 

66.68 

62.91 

Alumina 

14.27 

15  11 

15  00 

14  36 

15  98 

14  93 

19  13 

Ferric  oxide    .  .  . 

0.59 

0.77 

2.07 

0.75 

1  58 

0  98 

Ferrous  oxide  ...         

0.51 

1.02 

1.12 

2.78 

1.84 

3.32 

3  30 

Lime  

0.48 

1.65 

2.50 

1.58 

2.60 

4.89 

4.28 

Magnesia  

0.16 

0.30 

0.51 

1.17 

0.77 

2.19 

1.69 

Potash 

5  36 

4  33 

4  75 

3  28 

3  59 

2  05 

3  38 

Soda 

3  06 

3  92 

3  09 

1  95 

3  83 

2.65 

3  94 

Water  . 

0.92 

0.47 

0.64 

1.30 

0.45 

1.25 

0.63 

All  of  the  above  analyses  are  by  W.  F.  Hillebrand,  and  are  quoted  from 
15th  An.  Rep.  U.  S.  Geol.  Survey,  page  672.    The  localities  were  as  follows: 

1.  White  granite,  Brookville,  Montgomery  County. 

2.  Biotite-muscovite  granite,  Guilford,  Howard  County. 

3.  Biotite  granite,  Woodstock,  Baltimore  County. 

4.  Biotite  granite,  Sykesville,  Carroll  County. 

5.  Biotite  granite,  Dorsey  Run  Cut,  Howard  County. 

6.  Biotite  granite,  Rowlandsville,  Cecil  County. 

7.  Biotite  granite,  Dorsey  Run  Cut,  Howard  County. 

TABLE   17.— ANALYSES  OF  GNEISSES:  MARYLAND  AND 
DISTRICT  OF  COLUMBIA. 


i 

2 

3 

4 

5 

Silica 

73.69 

69.33 

67.22 

63.43 

78.28 

Alumina                           .  . 

12.89 

14.33 

15.34 

16.69 

9.96 

Ferric  oxide  

1.02 

2.78 

3.36 

1.85 

Ferrous  oxide  
Lime  

2.59 
3.74 

3.60 
3.21 

3.41 
1.36 

3.87 
0.80 

1.78 
1.68 

IMagnesia 

0.50 

2.44 

1.65 

2.33 

0.95 

Potash  .                     

1.48 

2.67 

3.26 

3.22 

1.35 

Soda      

2.81 

2.70 

2.00 

2.38 

2.73 

Water  

1.06 

1.22 

1.97 

2.90 

0.95 

1.  Biotite   gneiss,   Port   Deposit,   Cecil   County,    Md.     Wm.   Bromwell, 

analyst.     20th  Ann.  Rep.  U.  S.  Geol.  Surv.,  pt.  6,  p.  399. 

2.  Biotite  gneiss,  Broad  Branch  quarry,  District  of  Columbia.     W.  F. 

Hillebrand,  analyst;  15th  An.  Rep.  U.  S.  Geol.  Surv.,  p.  672. 


GRANITES  AND  OTHER  ACID  ROCKS 


49 


3.  Potomac  Stone  Company  quarry,  below  Chain  Bridge,  D.  C.     Ibid, 

p.  670. 

4.  Emery's  Store,  Cabin  John  Bridge,  Montgomery  County,  Md.     Ibid, 

p.  670. 

5.  Great  Falls,  Montgomery  County,  Md.     Ibid,  p.  670. 

TABLE   18.  — ANALYSES  OF  GRANITES:  VIRGINIA. 


1 

2 

3 

4 

5 

6 

7 

8 

9 

10 

Average 

of  1-8. 

Silica  

72.27 

71.51 

71.19 

70.83 

69.48 

69.44 

69.29 

68.45 

60.52 

58.32 

70.787 

Alumina  .  . 

14.30 

13.82 

14.01 

12.70 

13.95 

15.46 

14.07 

10.00 

16.99 

15.77 

14.04 

Ferric  ox. 

1.16 

1.76 

1.66 

2.67 

2.82 

1.31 

2.59 

5.71 

0.60 

6.56 

1.897 

Ferrous  ox. 

0.97 

1.20 

1.29 

1.36 

1.70 

1.43 

2.03 

2.59 

6.53 

0.59 

1.325 

Lime  

1.56 

1.79 

2.04 

1.88 

2.81 

2.11 

2.67 

6.20 

4.58 

11.58 

2.032 

Magnesia  .' 

0.70 

0.80 

0.14 

0.53 

1.10 

1.01 

1.32 

3.26 

1.59 

0.09 

0.763 

Potash  .  .  . 

5.00 

4.63 

4.45 

4.83 

3.45 

4.25 

2.87 

1.18 

3.91 

4.01 

4.435 

Soda  .  .  . 

3.45 

3.64 

3.56 

3.49 

3  65 

3  97 

2.89 

1.98 

2.83 

0.32 

3.628 

Water  .... 

0.29 

0.48 

0.37 

0.41 

0.54 

0.36 

0.43 

0.80 

0.88 

1.73 

0.408 

All  the  above  analyses  are  quoted  from  Bulletin  426,  U.  S.  Geol.  Survey, 
pages  72  and  78.  Analyses  1  to  8  inclusive  are  by  M.  W.  Thornton;  analyses  9 
and  10  by  W.  C.  Phalen.  The  localities  are  as  follows: 

1.  Biotite  granite,  Westham  quarries,  Richmond,  Chesterfield  County. 

2.  Biotite  granite,  Petersburg  Granite  Co.,  Petersburg,  Dinwiddie  County. 

3.  Biotite  granite,  McGowan  quarry,  Chesterfield  County. 

4.  Biotite  granite,  Netherwood  quarry,  Chesterfield  County. 

5.  Biotite    granite,    Cartwright    and    Davis    quarries,    Fredericksburg, 

Spottsylvania  County. 

7.  Biotite  gneiss,  Middendorf  quarry,  Manchester,  Chesterfield  County. 

8.  Biotite  gneiss,  Cartwright  and  Davis  quarries,  Fredericksburg,  Spott- 

sylvania County. 

9.  Pyroxene  syenite,  Milams  Gap,  Page  County. 
10.  Epidote  granite,  Milams  Gap,  Page  County. 


TABLE   19.  — ANALYSES  OF  GRANITES:   NORTH  CAROLINA. 


1 

2 

3 

4 

5 

6 

Silica  

75.92 

75.14 

71.56 

70.70- 

69.28 

66.01 

Alumina  

14.47 

n.d. 

16.79 

n.d. 

17.44 

n.d. 

Ferric  oxide 

0  88 

n.d. 

1  87 

n.d. 

1  08 

n.d. 

Ferrous  oxide 

n.d. 

n.d. 

1  22 

n.d. 

Lime  ... 

0  02 

0.93 

2.93 

2  96 

2  30 

1  44 

Magnesia  

0.09 

n.d. 

0.30 

n.d. 

0  27 

n.d. 

Potash  

4.01 

2.57  ) 

(  2.45 

2.76 

3.16 

Soda  
Water  

4.98 
0.64 

5.82  j 
n.d. 

11.96 
n.d. 

H.56 
n.d. 

3.64 
n.d. 

5.06 
n.d. 

50 


BUILDING  STONES  AND  CLAYS 


1.  Quartz  porphyry;  Charlotte,   Mecklenburg  County;  Genth,  analyst; 

Geology  of  North  Carolina,  Vol.  1,  p.  124. 

2.  Pink  Granite  Company,  quarry,  Dunn's  Mt.,  Rowan  County,  Bull. 

426,  U.  S.  Geol.  Surv.,  p.  117. 

3.  Granite;  Mount  Airy,  Surry  County;  C.  M.  Cresson,   analyst;   18th 

An.  Rep.  U.  S.  Geol.  Surv.,  pt.  5,  p.  970. 

4.  Granite;  Mount  Airy,  Surry  County;  Bull.  426,  U.  S.  Geol.  Surv.,  p.  117. 

5.  Granite;  Raleigh,  Wake  County;  Hanna,  analyst;  Geology  of  North 

Carolina,  vol.  1,  p.  302. 

6.  Granite;    Johnson    quarry,    Mooresville,    Iredell    County;    Bull.    426, 

U.  S.  G.  S.,  p.  117. 


TABLE  20.  — ANALYSES  OF  GRANITES:  SOUTH  CAROLINA. 


* 

2 

3 

4 

5 

6 

7 

8 

9 

10 

Silica  

68.70 

68.71 

68  8f 

68.90 

59  52 

69  74 

70  11 

70  2C 

70  54 

70  77 

Alumina  

15.49 

15.41 

15  7? 

15.75 

16.77 

13.72 

15  76 

14  22 

14  56 

14  89 

Ferric  oxide  .  . 

1.10 

1.85 

2.14 

1.16 

0.95  ( 

3AA 

(  1.07 

1.14 

1.06 

0.75 

Ferrous  oxide  . 

3.73 

1.59 

1.57 

1.49 

1.56) 

.04 

)  1.76 

1.24 

1.62 

1.24 

Lime  

1.70 

1.64 

1.64 

2.66 

1.82 

1.54 

1.84 

2.14 

1.28 

2.08 

Magnesia  

0.86 

1.25 

i.ie 

0.74 

0.75 

0.22 

0.62 

0.48 

0.78 

0.43 

Potash 

3  36 

4  61 

4  5^ 

1:      3   '49 

4  10 

4  98 

4  27 

4  82 

5  37 

4  70 

Soda.  .  . 

3  09 

3  48 

3  4£ 

4  76 

3  43 

5  39 

3  3C 

5  3S 

3  97 

4  47 

Water  

0.81 

0.34 

0.32 

.   0.18 

1.43 

0.45 

0.33 

0.27 

0.19 

11 

12 

13 

14 

15 

16 

17 

18 

19 

Aver- 
age. 

Silica  

70.90 

71.20 

72.19 

72.22 

73.26 

62.34 

65.72 

58.15 

73.10 

70.384 

Alumina.  . 

15.25 

17.04 

14.06 

14.51 

15.39 

17.22 

17.22 

14.30 

13.82 

15.237 

Ferric  ox. 
Ferrous  ox. 

1.52  I 
1.53  f 

3.48 

j  0.70 
I  1.80 

1.28) 
1.52$ 

1.24 

j  1.75 
12.49 

1.70 
2.67 

2.44 
2.49 

0.93 
1.43 

1.795 
2.477 

Lime  

2.40 

n.d. 

1.88 

1.32 

1.36 

3.28 

2.80 

2.80 

1.72 

1.807 

Magnesia. 

0.63 

0.11 

0.84 

0.58 

0.38 

1.30 

1.45 

1.04 

0.51 

0.655 

Potash  .    . 

2.85 

4.70 

3.94 

4.30 

6.89 

5.14 

3.80 

3.84 

5.06 

4.461 

Soda  

4.32 

2.32 

3.46 

3.21 

0.55 

5.28 

3.68 

3.80 

3.04 

3.645 

Water  .... 

0.17 

0.63 

0.18 

0.52 

n.d. 

0.28 

0.35 

0.28 

0.23 

0.448 

All  of  the  above  analyses  are  quoted  from  Bulletin  426,  U.  S.  Geol.  Survey, 
pages  174-175.     The  localities  are  as  follows: 

1.  Porphyritic  biotite  granite,  Clouds  Creek,  near  Batesburg,  Saluda 

County. 

2.  Porphyritic  biotite  granite,  Flat  Rock,  Kershaw  County. 

3.  Biotite  granite,  Cold  Point  Station,  Laurens  County. 

4.  Biotite  granite,  Jackson  quarry,  Clover,  York  County. 

5.  Biotite  granite,  Leitzsey  quarry,  Newberry,  Newberry  County. 

6.  Biotite  granite,  Anderson  quarry,  Rion,  Fairfield  County. 

7.  Biotite  granite,  Excelsior  quarry,  Heath  Springs,  Lancaster  County. 


GRANITES  AND  OTHER  ACID  ROCKS 


51 


8.  Biotite  granite,  Flatrock  quarry,  Carlisle,  Union  County. 

9.  Biotite  granite,  Benjamin  quarry,  Greenwood,  Greenwood  County. 

10.  Muscovite-biotite  granite,  Whiteside  quarry,  Filbert,  York  County. 

11.  Muscovite-biotite  granite,  Blair,  Fairfield  County. 

12.  Biotite  granite,   Keystone  Granite  Company,   Pacolet,   Spartanburg 

County. 

13.  Biotite  granite,  Ross  quarry,  Columbia,  Lexington  County. 

14.  Biotite  granite,  Southern  Granite  Company,  Heath  Springs,  Kershaw 

County. 

15.  Biotite  granite,  Winnsboro  Granite  Company,  Rion,  Fairfield  County. 

16.  Biotite  gneiss,  Hanckel  quarry,  Pendleton,  Anderson  County. 

17.  Biotite  gneiss,  Ware  Shoals,  Laurens  and  Abbeville  Counties. 

18.  Biotite  gneiss,  Beverly,  Pickens  County. 

19.  Biotite  gneiss,  Bates  quarry,  Batesburg,  Lexington  County. 


TABLE  21.— ANALYSES  OF  GRANITES:  GEORGIA. 


' 

2 

3 

4 

5 

6 

7 

8 

9 

10 

Silica 

72.56 
14.81 
0.94 
1.19 
0.20 
5.30 
4.94 
0.70 

71.00 
16.33 
1.12 
1.83 
0.35 
4.65 
4.80 
0.87 

70.38 
16.47 
1.17 
1.72 
0.31 
5.62 
4.98 
0.31 

70.30 
16.17 
1.19 
2.61 
0.31 
4.88 
4.72 
0.63 

70.18 
17.30 
1.20 
2.03 
0.64 
4.77 
4.36 
0.35 

70.03 
15.62 
1.31 
2.45 
0.52 
5.42 
4.22 
0.77 

69.88 
16.42 
1.96 
1.78 
0.36 
5.63 
4.45 
0.39 

69.74 
16.72 
1.45 
1.93 
0.36 
5.33 
4.84 
0.47 

69.64 
17.21 
1.32 
2.14 
0.66 
4.95 
4.53 
0.35 

69.55 
16.72 
0.99 
1.69 
0.27 
3.94 
5.88 
0.27 

Alumina  
Ferric  oxide  
Lime  
Magnesia  
Potash  

Soda 

Water  

11 

12 

13 

14 

15 

16 

17 

18 

19 

20 

Silica  
Alumina  
Ferric  oxide  
Lime  
Magnesia  
Potash  
Soda  
Water.... 

69.53 
16.46 
1.15 
2.10 
0.85 
4.91 
5.00 
0.91 

69.45 
15.93 
1.31 
1.91 
0.55 
5.16 
4.33 
0.50 

69.36 
17.23 
1.43 
2.14 
0.59 
4.57 
5.17 
0.33 

69.34 
17.01 
1.74 
2.77 
0.61 
4.54 
4.69 
0.26 

69.25 
16.04 
1.72 
1.89 
0.31 
4.94 
4.52 
0.43 

69.08 
17.67 
1.41 
3.27 
0.64 
3.29 
4.56 
0.56 

69.07 
16.56 
1.37 
1.83 
0.76 
5.02 
4.65 
0.92 

68.81 
17.67 
1.13 
2.17 
0.50 
3.90 
4.97 
0.30 

68.79 
16.48 
0.98 
1.76 
1.30 
5.85 
4.74 
0.38 

68.76 
16.80 
0.99 
2.72 
1.00 
3.70 
4.82 
0.29 

21 

22 

23 

24 

25 

26 

27 

28 

29 

30 

Silica  
Alumina 

68.38 
17.79 
1.21 
2.85 
0.72 
3.57 
4.36 
0.78 

66.92 
18.19 
3.05 
4.95 
1.25 
2.02 
3.83 
0.46 

63.27 
19.93 
2.82 
2.89 
0.49 
4.85 
4.14 
0.86 

70.90 
15.86 
1.37 
2.15 
0.02 
4.62 
5.05 
0.50 

70.88 
15.86 
1.77 
1.79 
0.93 
4.64 
3.94 
0.49 

70.24 
16.78 
1.46 
2.00 
0.76 
5.03 
3.70 
0.50 

69.77 
17.05 
1.60 
2.21 
0.99 
4.08 
3.97 
0.44 

69.48 
16.64 
1.84 
2.32 
0.29 
4.49 
4.74 
0.46 

69.37 
16.99 
1.99 
2.03 
0.84 
4.54 
3.44 
0.55 

69.17 
16.47 
1.22 
2.02 
0.61 
4.41 
4.89 
1.06 

Ferric  oxide  
Lime  
Magnesia  
Potash  
Soda 

Water  

BUILDING  STONES  AND  CLAYS 


TABLE  21  (Continued) 


31 

32 

33 

34 

35 

36 

37 

38 

39 

40 

Silica  

69.13 
17.14 
1.52 
1.85 
0.79 
5.49 
4.06 
0.52 

67.62 
16.29 
2.31 
2.37 
0.78 
4.58 
5.42 
0.32 

66.31 
18.27 
2.51 
2.91 
1.22 
4.09 
3.69 
0.61 

63.65 
20.46 
2.20 
3.38 
1.50 
4.58 
4.75 
0.42 

76.37 
13.31 
1.21 
1.13 
0.10 
3.68 
4.02 
0.20 

76.00 
13.11 
0.92 
1.06 
0.27 
4.69 
3.88 
0.31 

75.89 
14.02 
0.71 
0.70 
0.12 
5.56 
3.64 
0.28 

75.45 
13.71 
0.92 
0.94 
0.18 
4.30 
3.87 
0.40 

75.16 
13.74 
0.91 
0.91 
0.17 
5.05 
3.76 
0.32 

74.96 
13.71 
0.90 
1.02 
0.24 
4.79 
4.68 
0.44 

Alumina         

Ferric  oxide  
Lime  
Magnesia  
Potash  
Soda 

Water  

41 

42 

43 

44 

45 

46 

Silica                   

74.80 
15.46 
1.04 
0.82 
0.11 
2.52 
4.80 
0.31 

73.95 
14.23 
1.29 
1.07 
0.23  • 
5.29 
4.61 
0.25 

72.96 
14.70 
1.28 
1.28 
0.07 
4.73 
4.18 
0.23 

71.20 
15.46 
1.17 
1.36 
0.38 
5.30 
4.96 
0.52 

69.51 
16.32 
2.38 
1.84 
1.28 
3.47 
3.82 
1.11 

68.89 
16.47 
2.34 
1.63 
0.40 
4.15 
4.38 
0.32 

Alumina  
Ferric  oxide 

Lime 

Magnesia 

Potash                       .  .                 ... 

Soda  
Water  

Analyses  1  to  46  of  the  preceding  table  are  quoted  from  Watson's  report  on 
the  granites  of  Georgia,  published  as  Bulletin  9,  Georgia  Geological  Survey. 
All  were  made  by  T.  L.  Watson,  on  samples  collected  by  himself.  Nos.  1  to 
23  inclusive  are  of  normal  granites;  Nos.  24  to  34  are  of  porphyritic  granites; 
and  Nos.  35  to  46  of  gneisses.  The  localities  from  which  the  various  samples 
were  taken  are  as  follows: 

1.  Stone  Mountain,  DeKalb  County. 

2.  Fortson  quarry,  near  Goss,  Elbert  County. 

3.  Coggins  Granite  Company,  near  Elberton,  Elbert  County. 

4.  Diamond  Blue  Granite  Company,  Hutchins,  Oglethorpe  County. 

5.  Brown-Dead wyler  quarry,  in  Madison  County. 

6.  Lexington  Blue  Granite  Company  quarry,  Oglethorpe  County. 

7.  Greenville  Granite  County  quarry,  Meriwether  County. 

8.  9.   Coggins  Granite  Company  quarry,  near  Oglesby,  Elbert  County. 

10.  Carmichael  quarry,  Fairburn,  Campbell  County. 

11.  Hutchins,  Oglethorpe  County. 

12.  Swift  &  Wilcox  quarry,  Elberton,  Elbert  County. 

13.  Childs  quarry,  Oglesby,  Elbert  County. 

14.  Linch  quarry,  Eatonton,  Putnam  County. 

15.  Tate  &  Oliver  quarry,  Elberton,  Elbert  County. 

16.  Cole  quarry,  Newman,  Coweta  County. 

17.  Overby  quarry,  Coweta  County. 

18.  Echols  Mill,  Oglethorpe  County. 

19.  Hill  quarry,  Newman,  Coweta  County. 

20.  Turner  quarry,  Griffin,  Spalding  County. 


GRANITES  AND  OTHER  ACID  ROCKS 


53 


21.  Camak,  Warren  County. 

22.  Grantville,  Coweta  County. 

23.  Tigner  quarry,  Odessa,  Meri wether  County. 

24.  Georgia  Quincy  Granite  Company  quarry,  Sparta,  Hancock  County. 

25.  Lime  Creek,  Fayette  County. 

26.  Flat  Rock,  Pike  County. 

27.  Heggie  Rock,  Columbia  County. 

28.  Sparta  quarry,  Hancock  County. 

29.  Milledgeville,  Baldwin  County. 

30.  Moseley  quarry,  East  Point,  Fulton  County. 

31.  Greensboro,  Greene  County. 

32.  Rocker  quarry,  Hancock  County. 

33.  Brinkley  property,  Warren  County. 

34.  McCollum  quarry,  Coweta,  Coweta  County. 

35.  Odessa  quarry,  Meriwether  County. 

36.  Crossley  quarry,  Lithonia,  Dekalb  County. 

37.  Snell  quarry,  Snellville,  Gwinnett  County. 

38.  Tilley  quarry,  Rockdale  County. 

39.  Arabia  Mountain,  Lithonia,  Dekalb  County. 

40.  Flat  Rock,  near  Franklin,  Heard  County. 

41.  Flat  Shoals,  Meriweather  Co. 

42.  Flat  Rock,  Coweta  County. 

43.  Southern  Granite  Company  quarry,  Lithonia,  Dekalb  County. 

44.  Freeman  quarry,  Covington,  Newton  County. 

45.  Athens,  Clarke  County. 

46.  McElvaney  Shoals,  Gwinnett  County. 


TABLE  22.  — ANALYSES  OF  GRANITES:    ARKANSAS, 
MISSOURI  AND  OKLAHOMA. 


Constituent. 

l 

2 

3 

4 

5 

6 

7 

8 

9 

Silica 

60.03 
20.76 
4.01 
0.75 

59.62 
18.67 
5.07 

59.70 

18.85 
4.85 

72.35 

13.78 
1.87 
0.36 
0.87 
0.42 
4.49 
4.44 
0.76 

71.88 
12.88 
3.05 
1.05 
1.13 
0.33 
4.46 
4.21 
0.43 

71.33 
12.55 
3.75 
0.85 
0.94 
0.58 
4.20 
4.52 
0.42 

69.94 
15.19 
1.88 
0.60 
1.15 
0.92 
4.29 
3.95 
0.99 

77.05 
11.77 
2.33 
n.d. 
2.21 
n.d. 
3.88 
2.90 
0.52 

65.30 
19.94 
2.60 

4L50 
1.00 

J4.37 
0.30 

Alumina            

Ferric  oxide  
Ferrous  oxide  

Lime  

2.62 
0.80 
5.48 
5.96 

1.80 
0.84 
5.65 
6.95 
0.80 

1.34 
0.68 
5.97 
6.29 

1.88 

Magnesia 

Potash   .  . 

Soda   .  .             .... 

Water  

1.  Elaeolite  syenite,  Fourche  Mt.,  Ark.;    R.  N.  Brackett,  analyst;   An. 

Rep.  Ark.  Geol.  Sur.  for  1890,  vol.  2,  p.  39. 

2.  Elaeolite  syenite,  Bauxite  Station,  Ark.;  W.  A.  Noyes,  analyst;  An. 

Rep.  Ark.  Geol.  Sur.  for  1890,  vol.  2,  p.  135. 

3.  Elaeolite  syenite,  Fourche  Mt.,  Ark.;  W.  A.  Noyes,  analyst;    An.  Rep. 

Ark.  Geol.  Sur.  for  1890,  vol.  2,  p.  181 


54 


BUILDING  STONES  AND  CLAYS 


4.  Granite,   Ironton,  Mo.;   W.  Melville,   analyst;    Prof.   Paper,  No.   14, 

U.  S.  Geol.  Sur.,  p.  147. 

5,  6.   Quartz  porphyry,  Ironton,  Mo.;  W.  Melville,  analyst;   Ibid. 

7.  Granite,  Ironton,  Mo.;  Ibid,  p.  161. 

8.  Granite,    Graniteville,   Mo.;    W.    Melville,    analyst;  18th    An.    Rep. 

U.  S.  Geol.  Sur.,  pt.  5,  p.  968. 

9.  Tishomingo,  Oklahoma;  Min.  Resources  U.  S.,  for  1903. 

TABLE  23.  — ANALYSES  OF   GRANITE:   WISCONSIN. 


1 

2 

3 

4 

5 

6 

7 

Aver- 
age. 

Silica  (SiO2). 

76.54 

66.10 

75.40 

74.62 

76.62 

73  65 

73  09 

73  717 

Alumina  (A^Os)  .  .  . 
Ferric  oxide  (Fe2O3) 
Ferrous  oxide  

13.82 
1.62 

20.82 
1.52 
2.17 

11.34 
4.16 

10.01 
3.85 
1.72 

13.02 
1.01 

11.19 
1.31 
3.25 

13.43 
2.57 

13.376 
1.604 
1.020 

Lime 

0  85 

1  57 

0.90 

2  43 

0  51 

2  78 

2  29 

1  619 

Magnesia 

0.01 

0  95 

0  33 

0  05 

0  51 

1  03 

0  412 

Potash  

2.31 

3.48 

6.44 

3.38 

6.38 

1.86 

1  58 

3  633 

Soda  
Water 

4.32 
0  20 

2.94 
0  54 

1.76 

3.33 
0  24 

2.24 

3.74 
0  44 

3.85 
0  72 

3.169 
0  428 

1.  Wausau,  W.  W.  Daniells,  analyst;  Bull.  4,  Wis.  Geol.  Sur.,  p.  420. 

2.  Athelstane,  W.  W.  Daniells,  analyst;  Bull.  4,  Wis.  Geol.  Sur.,  p.  420. 

3.  Montello,  F.  G.  Weichmann,  analyst;  Bull.  4,  Wis.  Geol.  Sur.,  p.  420. 

4.  Waushara,  S.  Weidman,  analyst;  Bull.  4,  Wis.  Geol.  Surv.,  p.  420. 

5.  Waushara,  Milwaukee  Monument  Company,  A.  S.  Mitchell,  analyst; 

Min.  Res.  U.  S.,  1903,  p.  204. 

6.  Berlin,  S.  Weidman,  analyst;  Bull.  4,  Wis.  Geol.  Surv.,  p.  420. 

7.  Uttley,  S.  Weidman,  analyst;  Bull.  4,  Wis.  Geol.  Sur.,  p.  420. 

TABLE  24.— ANALYSES  OF  GRANITE:    WESTERN  AND 
PACIFIC  STATES. 


Constituent. 

1 

2 

3 

4 

5 

6 

7 

8 

9 

Silica  

75.35 

61.47 

58.67 

68.50 

71.78 

68.24 

71.70 

71.98 

67.45 

Alumina  

13.69 

23.02 

14.89 

17.02 

14.75 

16.30 

14.54 

15.07 

13.04 

Ferric  oxide     ) 
Ferrous  oxide  )  ' 

3.94 

4.46 

7.56J 

3.25 

i!94 

1.37 
2.13 

1.46 
1.80 

1.97 
0.82 

5.56 

2.78 

Lime  

2.97 

5.59 

5.68 

4.66 

2.36 

3.20 

3.13 

2.46 

4.68 

Magnesia  

0.06 

trace 

1.79 

1.58 

0.71 

1.88 

0.39 

0.58 

2.65 

Potash  
Soda 

2.85 
1  14 

1.22 
4  09 

2.69 
7  69 

2.10 
3.55 

4.89 
3.12 

|e.3o 

6.06 

6.92 

3.57 

Water  

0.57 

0.52 

0.24 

0.92 

0.20 

0.27 

/ 

'  re 

1.  Exeter,  Tulare  County,  Calif.;  Watertown  Arsenal,  analyst;  Min.  Res. 

U.  S.,  1903. 

2.  Snake  River,  Nez  Percys  County,  Idaho;    W.  C.  Day,  analyst;  Min. 

Res.  U.  S.,  1903. 


GRANITES  AND  OTHER  ACID  ROCKS 


55 


3.  Reno,  Washoe  County,  Nevada;  J.  W.  Phillips,  analyst;  20th  An.  Rep. 

U.  S.,  pt.  6,  p.  416. 

4.  Haines,  Baker  County,  Oregon;  Watertown  Arsenal,  analyst;  Min.  Res. 

U.  S.,  1903. 

5.  Little  Cottonwood  Canyon,  Utah;  T.   M.   Drown,  analyst;  Reports 

Fortieth  Parallel  Survey,  vol.  2,  p.  356. 

6.  Medical  Lake,  Washington;  R.  W.  Thatcher,  analyst;  vol.  2,  Reports 

Washington  Geol.  Sur.,  p.  141. 

7.  Snake  River,  Washington;  ibid. 

8.  Little  Spokane  River,  Washington;  ibid. 

9.  Index,  Washington;  ibid. 


PHYSICAL  PROPERTIES  OF  GRANITES. 

Density.  —  Data  regarding  the  specific  gravity  and  weight 
per  cubic  foot  of  granites  are  available  in  sufficient  quantity  to 
serve  as  bases  for  general  conclusions.  With  regard  to  absorp- 
tion and  porosity  this  is  not  the  case,  for  here  the  methods  of 
testing  differ  so  widely  that  no  general  comparisons  can  be  made. 


TABLE  25.— AVERAGE  SPECIFIC  GRAVITY 
OF  GRANITES. 


AND  WEIGHT 


Results  averaged. 

Specific  gravity. 

Weight  per 
cubic  foot, 
average. 

Minimum. 

Average. 

Maximum. 

12  New  England  granites  

2.618 
2.645 
2.629 

2.644 
2.677 
2.655 

2.671 
2.739 
2.713 

17  Georgia  granites 

14  Wisconsin  granites   .    . 

Final  results,  average 

2.618 

2.659 

2.739 

165.92 

Compressive  Strength  of  Granites.  —  In  a  preceding  section 
it  was  noted  that  the  variations  in  chemical  analyses  of  granites 
seemed,  at  first  sight,  to  be  so  great  as  to  defy  any  attempt  to 
generalize  concerning  normal  composition;  but  that  careful  ex- 
amination showed  that  the  difficulty  was  not  insurmountable. 
The  same  things  can  be  said,  with  equal  truth,  regarding  the 
compressive  strength  of  granites. 

In  the  table  (Table  27)  presented  later,  the  results  of  com- 
pression tests  on  seventy-five  American  granites  are  tabulated. 
These  present  wide  variations,  the  lowest  test  reported  in  the 
table  showing  only  5657  pounds  per  square  inch,  while  the 


56  BUILDING  STONES  AND  CLAYS 

highest  result  is  47,674  pounds.  If  we  take  the  column  of 
averages,  however,  it  is  soon  found  that  these  extreme  results* 
do  not  fairly  represent  the  situation.  In  the  following  table 
the  tests  are  grouped  into  classes,  according  to  average  results. 


TABLE  26.  — AVERAGE  COMPRESSIVE  STRENGTH  OF 
GRANITES. 

Class.  Number  of  tests. 

Below  15,000  Ibs.  per  square  inch 7 

Between  15,000  and  20,000  Ibs 16 

Between  20,000  and  25,000  Ibs 30 

Between  25,000  and  30,000  Ibs 12 

Over  30,000  Ibs.  per  square  inch 10 

Total  tests  75 

From  this  grouping  it  can  be  inferred  that  the  average  granite 
will  fall  within  the  third  class  of  the  above  table.  As  a  matter 
of  fact,  the  arithmetical  average  of  all  of  the  seventy-five  tests 
recorded  in  Table  27  is  actually  23,228  pounds  per  square  inch. 

*  The  low  results  are  on  schists  and  poor  gneisses;  the  highest  results  are 
the  remarkable  tests  reported  by  the  Wisconsin  Geological  Survey. 


GRANITES  AND   OTHER  ACID  ROCKS 


57 


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GRANITES  AND  OTHER  ACID  ROCKS 


59 


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60 


BUILDING  STONES  AND   CLAYS 


TABLE  28.— TRANSVERSE  STRENGTH  OF  GRANITES. 


1 

. 

4 

. 

I 

- 

0 

State. 

Locality. 

Tested  by 

•3 

1 

1 

§• 

I 

•a 

1 

M 

° 

* 

•< 

• 

In. 

In. 

In. 

Arkansas  

Watertown 

5 

20 

4 

6 

1067 

1400 

1755 

California  

Exeter  

Watertown 

20 

4 

6 

1853 

Georgia  

Stone  Mt.  . 

Watertown 

20 

6 

6 

2610 

Maine  

Millbridge. 

Watertown 

"2" 

20 

4 

6 

2027 

2048 

2069 

Massachusetts  . 

Cape  Ann  .  . 

Watertown 

19 

4 

6 

2392 

Wisconsin.  . 

Montello  .  . 

Buckley.  .  . 

2 

4 

1 

1 

3678 

3794 

3910 

it 

New  Hill.. 

Buckley.  .  . 

2 

4 

1 

1 

2324 

2519 

2713 

TABLE  29.  — PHYSICAL  PROPERTIES  OF  ENGLISH 
GRANITES  (BEARE). 


Specific 
gravity. 

Weight. 

Absorb. 

Penrhyn 

2.65 

165  4 

0   12 

16,490 

Cornwall  

2.59 

161.7 

14,870 

Aberdeenshire: 
Corennie 

2  58 

161  0 

0  40 

19  855 

Cove 

2  71 

169  1 

0  55 

15  355 

Kemnay 

2  605 

162  5 

0  32 

17  880 

Craigton  . 

19  935 

Peterhead  

2.54 

158.5 

0  29 

18,785 

Dyce  

2.65 

165.4 

0.19 

17,200 

Hill  of  Fare  

2.55 

159.1 

0.40 

21,160 

Sclattie 

2  58 

161  0 

0  10 

13  230 

Persley 

2  60 

162  3 

0  19 

14  665 

Rubislaw  

2.623 

163.7 

0  09 

18  575 

Ben  Cruachan  

2.75 

171.6 

0.29 

13,640 

Geological  Distribution  of  Granites.  —  Rocks  of  granitic  type 
may  have  formed  the  greater  proportion  of  the  original  crust  of 
the  earth,  but  it  is  improbable  that  any  of  these  first-formed 
granites  are  now  exposed  at  the  surface.  Granites  and  granitic 
gneisses,  however,  undoubtedly  still  make  up  the  major  portion 
of  the  pre-Cambrian  rocks,  so  far  as  these  rocks  are  now  open  to 
inspection.  And  in  all  of  the  geologic  periods,  from  the  pre- 
Cambrian  to  the  Tertiary,  masses  of  granite  and  allied  rocks 
have  been  intruded  into  the  existing  formations.  The  result  of 
this  history  is  that,  among  the  granites  exposed  at  the  surface 
to-day,  almost  every  geologic  age  is  represented  in  some  part 


GRANITES  AND  OTHER  ACID  ROCKS 


61 


of  the  world.  When  looked  at  in  this  broad  fashion,  little  definite 
can  be  said  regarding  the  geologic  age  of  granites;  but  when  the 
inquiry  is  limited  to  smaller  areas  the  question  of  age  admits 
of  discussion. 

The  area  which  supplies  by  far  the  bulk  of  American  commer- 
cial granites,  for  example,  is  that  located  in  New  England.  The 
southward  extension  of  the  same  area  along  the  Blue  Ridge  and 
Appalachian  regions  promises  to  become  of  greater  industrial 
importance  yearly.  In  both  of  these  areas,  a  relatively  small 
portion  of  the  granites  and  gneisses  quarried  are  of  pre-Cambrian 
age.  The  bulk  of  the  commercial  granites  is  derived  from  masses 
intruded  into  pre-Cambrian  or  later  rocks  during  the  Silurian, 
Devonian  and  Carboniferous  periods;  and  it  seems  probable 
that  most  of  these  intrusive  granites  date  back  only  to  the 
Carboniferous. 

In  the  western  states  a  greater  range  in  geologic  age  is  shown, 
and  here  no  general  statement  of  value  can  be  made,  owing  to 
the  relatively  small  development  of  the  granite  industry. 

Granites  do  not  occur  in  Ohio,  West  Virginia,  Tennessee, 
Indiana,  Illinois,  Florida,  Mississippi,  Louisiana,  Kansas,  Iowa, 
Nebraska  and  North  Dakota;  they  occur  at  only  one  or  two 
localities  in  South  Dakota  and  Kentucky;  and  in  small  areas 
only  in  Missouri,  Arkansas,  Texas  and  Oklahoma.  In  the 
remaining  states  rocks  of  granitic  type  cover  considerable  areas. 

Production  of  Granite  in  the  United  States.  —  The  following 
tables,  revised  slightly  from  those  published  by  the  United  States 
Geological  Survey,  give  statistics  concerning  the  granite  industry 
for  a  series  of  years.  It  is  to  be  noted,  however,  that  in  these 
tables  trap  and  other  basic  igneous  rocks  are  included  under 
the  general  head  of  "  granite  "  in  most  states. 

TABLE  30.  — GRANITE   PRODUCTION  OF  THE   UNITED 
STATES,    1899-1909. 


Year. 

Value. 

Year. 

Value. 

1899 

$10,343,298 

1905 

$17,563,139 

1900 

10,969,417 

1906 

18,562,806 

1901 

14,266,104 

1907 

18,064,708 

1902 

16,083,475 

1908 

18,420,080 

1903 

15,703,793 

1909 

19,581,597 

1904 

17,191,479 

1910 

20,541,967 

62 


BUILDING  STONES  AND  CLAYS 


TABLE  31.— GRANITE  PRODUCTION,  BY  STATES,   1905-1909. 


State  or  Territory. 

1905. 

1906. 

1907. 

1908. 

1909. 

Arizona  

$3,700 

$32,042 

$13,700 

$8,544 

(a) 

Arkansas  

90,312 

118,903 

168,996 

152,567 

$150  179 

California 

1  161  330 

'     740  784 

1  306  324 

1  684  504 

1  310  520 

Colorado 

73  802 

65402 

67  134 

121  282 

74  326 

Connecticut  
Delaware  . 

636,364 

178,428 

974,024 
146,346 

591,153 
158,192 

592,904 
195,761 

610,514 

456  328 

Georgia  

971,207 

792,315 

858,603 

970,832 

843,542 

Hawaii  

33,550 

23,346 

19,599 

81,219 

68,955 

Idaho  

1,500 

400 

25,942 

(a) 

(a) 

Maine 

2  713  795 

2  560  021 

2  146  420 

2  027  508 

1  939  524 

Maryland  
Massachusetts  . 

957,048 
2,251,319 

883,881 
3,327,416 

1,183,753 

2,328,777 

762,442 
2,027,463 

771,224 
2  164  619 

Michigan  

Minnesota  

481,908 

626,069 

546,603 

629,427 

i  b  660,823 

Missouri 

180  579 

150  009 

136  405 

157  968 

155  717 

Montana 

126  430 

114  005 

102  050 

(a)- 

(0) 

Nevada 

New  Hampshire  
New  Jersey  

838,371 
76,758 

818,131 
101,224 

647,721 

75,757 

867,028 
125,804 

1,215,461 
60,175 

New  Mexico 

167  294 

(a) 

New  York  

134,425 

304,048 

289,722 

367,066 

443,910 

North  Carolina  .... 
Oklahoma  
Oregon  . 

564,578 
20,720 
85,330 

778,847 
18,847 
58,961 

889,976 
24,550 
117,625 

764,272 
23,239 
271,869 

743,876 
67,584 
284,135 

Pennsylvania  

450,619 

349,453 

366,679 

324,241 

507,814 

Rhode  Island  

556,364 

622,812 

674,148 

556,474 

933,053 

South  Carolina  
South  Dakota 

297,284 

247,998 

129,377 
690 

297,874 

(a) 

218,045 

Texas 

132,193 

168,061 

122,158 

190,055 

173,271 

Utah  

13,630 

4,948 

5,240 

5,229 

7,525 

Vermont  

2,571,850 

2,934,825 

2,693,889 

2,451,933 

2,811,744 

Virginia  

452,390 

340,900 

398,426 

321,530 

488,250 

Washington 

681  730 

459  975 

562,352 

870,944 

742,878 

Wisconsin  
Wyoming  

825,625 

798,213 
600 

1,228,863 
90 

1,529,781 

(a) 

1,442,305 

Other  States  

40,320 

c  235,300 

Total  

17,563,139 

18,562,806 

18,064,708 

18,420,080 

19,581,597 

a  Included  in  "Other  States." 

b  Includes  a  small  value  for  trap  rock  in  Michigan  and  Minnesota. 

c  Includes  Arizona,  Idaho,  Montana,  and  New  Mexico. 


GRANITES  AND  OTHER  ACID  ROCKS 


63 


TABLE  32.  — GRANITE  PRODUCTION  OF   1909,   BY  STATES 

AND  USES. 


State  or  Territory. 

Sold  in  the  rough. 

Dressed 
for 
building 

Dressed 
for  mon- 
umental 
work. 

Made 
into 

Kg. 

Building. 

Monu- 
mental. 

Rubble. 

Riprap. 

Other. 

Arkansas  

$1,000 
30,536 
15,267 
25,097 
9,769 
39,685 
3,100 
237,597 
120,561 
212,075 
43,659 
4,093 
143,757 
7,366 
35,399 
56,859 
1,471 
6,996 
306,466 
45,501 
67,877 
29,530 
996 
128,233 
24,965 
11,478 
300 
2,502 

$39,579 
28,451 
35,867 

28,i74 

$9,522 
12,798 
4,950 
5,342 
1,557 
33,216 

$68,000 
109,847 
18 
112,830 
280,488 
59,245 

$799 
432,551 
24,000 
274,501 
2,043 
120,270 

$120 

97,978 

66,538 
2,693 

$34,476 

8,698 
9,084 
93,300 

California 

$2,875 
1,200 
1,382 

Colorado  

Connecticut 

Delaware  

Georgia  
Hawaii  

Maine  

31,375 
8,471 
508,805 
76,636 
46,750 
70,018 
1,000 
1,864 
11,682 
16,541 
5,460 
10,400 
176,565 
5,215 
36,082 
4,396 
1,154,826 
1,966 
6,308 
26,984 
8,940 

14,685 
70,479 
51,658 
48,210 

23,387 
150 
17,639 
5,803 
13,050 

4,75i 
1,510 
19,680 

14,090 
6,695 
2,462 
1,093 
3,878 
4,367 
200 
5,421 
34 
8,000 

53,637 
22,141 

4,166 
1,386 
18,408 

26,271 
4,450 
17,752 

1,152,677 
114,002 
542,441 
144,997 
5,930 
521,299 
1,133 
17,193 
142,778 
15,408 
2,321 
53,529 
218,089 
1,000 
36,612 

1,035,675 
17,750 
17,185 
5,154 
22,000 

39,704 
2,675 
298,235 
167,088 
2,300 
192,762 
50 
23,903 
38,192 
5,691 
16,129 

'  314,237 

ii',400 
2,133 
479,415 
9,449 
19,902 
212,043 
3,000 

262,895 
93,742 
308,203 
66,605 
46,163 
170,434 
2,250 
250,070 
214,508 

37,348 
15,840 
52,004 
4,284 

5,824 
18,053 
66,544 
982,798 

Maryland 

Massachusetts  
Minnesota  

Missouri  

New  Hampshire  
New  Jersey 

200 
942 
2,971 

New  York  
North  Carolina  
Oklahoma  
Oregon 

i',950 
73 
1,755 

2,875 

'"166 

Pennsylvania  

Rhode  Island  
South  Carolina  
Texas  
Utah  . 

i',037 
33,321 
423,230 
420 
1,000 

Vermont  

Virginia 

Washington  
Wisconsin  

•-    Other  States  
Total  

1,612,135 

2,342,355 

797,395 

775,740 

64,796 

4,920,737 

2,005,637 

2,743,117 

64 


BUILDING  STONES  AND  CLAYS 


TABLE  32.— GRANITE  PRODUCTION  OF  1909,  BY  STATES 
AND  USES.     (Concluded.} 


State  or  Territory. 

Curbing. 

Flagging. 

Crushed  stone. 

Other. 

Total. 

Road- 
making. 

Railroad 
ballast. 

Concrete. 

(a) 
$150,179 
1,310,520 
74,326 
610,514 
456,328 
843,542 
68,955 
(a) 
1,939,524 
771,224 
2,164,619 
(6) 
c  660,823 
155,717 
(a) 
1,215,461 
60,175 
(a) 
443,910 
743,876 
67,584 
284,135 
507,814 
933,053 
218,045 
173,271 
7,525 
2,811,744 
488,250 
742,878 
1,442,305 
235,300 

Arkansas  

$300 
163,012 

'"$375" 
'"256" 
'"246" 

"  13,770  " 
2,427 
3,666 

$68,338 
262,077 

'"7,834" 
20,105 
16,405 
40,855 

"  10,786" 
138,465 
56,805 

$1,470 
57,064 

$630 
65,020 

"$2,338" 
440 
2,850 
500 
996 

"52,756" 
8,739 
3,935 

""l',256" 
'"4,775" 

"i',923" 

"  17,31  1" 
19 
2,185 

'"56" 
4,400 
14,381 
45,460 
13,569 

California  

Connecticut  
Delaware 

45,573 
3,960 
318,957 

23,752 
30,337 

83,497 
25,000 

""7,849" 
158,468 
36,344 

98,485 
46,864 

'"336" 
38,576 
8,533 

Georgia  
Hawaii  
Idaho 

Maine  
Maryland  
Massachusetts  
Michigan        

74,739 
3,474 
113,705 

Minnesota 

8,154 

150 

40,221 
15,345 

"2l',429" 

26,220 

36,540 
31,258 

Missouri  

Montana 

New  Hampshire  
New  Jersey  

53,088 

635 

"44,966" 

'"2,666" 
28,151 

"i',025  ' 
5,625 
2,617 
15,827 

9,360 
2,124 

"  33',  235" 
101,866 
3,500 
5,480 
39,004 
17,125 
32,834 
947 

New  Mexico 

52,263 
44,617 

'206,372" 
41,047 
99,358 
10,672 
32,584 

New  York  

1,352 

North  Carolina  
Oklahoma 

98,153 
2,000 

"'8,461' 
5,955 
3,554 
1,100 

1,233 

""3,664" 
3,490 

'"w" 

Oregon  
Pennsylvania  
Rhode  Island  
South  Carolina  
Texas 

Utah  

Vermont 

1,319 
29,100 
76,574 
3,048 
15,100 

'"996" 

"  16,875" 

765 

74,054 
88,868 
125,838 
13,608 

1,000 
125,704 

Virginia  
Washington  
Wisconsin 

147,112 

'  155,581 

23,385 

Other  States  (<*)  
Total  

1,030,568 

47,230 

1,488,711 

660,632 

914,667 

177,877 

19,581,597 

o  Included  in  "  Other  States." 

6  A  small  value  for  trap  rock  included  in  Minnesota. 

c  Includes  a  value  of  trap  rock  for  Michigan  and  Minnesota. 

d  "  Other  States  "  includes  Arizona,  Idaho,  Montana,  and  New  Mexico. 


GRANITES  AND  OTHER  ACID  ROCKS 


65 


TABLE  33.  — NUMBER  AND   VALUE  OF  GRANITE   PAVING 

BLOCKS  PRODUCED  IN   1908  AND   1909,  BY  STATES 

AND  TERRITORIES. 


State  or  Territory. 

Paving  blocks. 

1908. 

1909. 

Number. 

Value. 

Number. 

Value. 

California                      

1,657,600 
292,485 
121,000 
4,735,770 
8,005,662 
692,538 
6,134,648 
532,750 
1,826,742 
2,842,206 
96,956 
1,573,777 
3,679,745 
5,900 
1,000,000 
529,037 
567,416 
351,250 
6,000 
58,200 
358,664 
3,000 
13,399,882 

$66,079 
14,951 
6,050 
135,510 
368,715 
71,316 
261,880 
35,750 
75,320 
103,833 
2,674 
98,273 
122,488 
400 
40,000 
23,628 
29,651 
12,277 
300 
1,547 
10,173 
255 
939,485 

817,500 
180,130 
187,095 
3,384,600 
6,137,682 
1,107,149 
6,878,872 
974,000 
1,150,914 
4,997,161 
30,000 
3,571,997 
5,062,500 

$34,470 
8,698 
9,084 
93,300 
262,895 
93,742 
308,203 
66,605 
46,163 
170,434 
2,250 
250,070 
214,508 

"37',348" 
15,840 
52,004 
4,284 

"5,824" 
18,053 
66,544 
982,798 

Connecticut     

Delaware  

Georgia  

Maine  

Maryland 

Massachusetts 

Minnesota 

Missouri 

New  Hampshire  
New  Jersey  
New  York  

North  Carolina 

Oklahoma 

Oregon 

936,260 
374,171 
1,051,681 
106,204 

'  '163,885 
853,300 
1,109,072 
18,798,977 

Pennsylvania.  . 

Rhode  Island  

South  Carolina  
Texas  

Vermont 

Virginia 

Washington 

Wisconsin 

Total 

48,471,228 

2,420,555 
49.94 

57,873,150 

2,743,117 
47.40 

Average  price  per  thousand  .... 

66 


BUILDING  STONES  AND  CLAYS 


TABLE  34.  —  PRODUCTION  OF  GRANITE  IN  VERMONT   IN 

1908  AND  1909,   BY  COUNTIES  AND  USES. 

1908. 


County. 

Number  of 
firms  re- 
porting. 

Building. 

Rough. 

Dressed. 

Quantity 
(cubic  feet)  . 

Value. 

Quantity 
(cubic  feet). 

Value. 

Washington  and  Orange  
Windsor  

39 
3 
9 
3 

15,896 
63,537 
12,753 
12,050 

$9,871 
59,054 
3,999 
6,787 

129,230 
52,866 

$429,967 
244,850 

Caledonia  and  Orleans  

Windham  

1,225 

1,250 

Total  

54 

104,236 

79,711 
.76 

173,321 

676,067 
3.90 

Average  price  per  cu.  ft.. 

Monumental. 

Other 

•„- 

Paving. 

pur- 

Rough. 

Dressed. 

poses. 

County. 

Total 

Quantity 
(cubic 
feet). 

Value. 

Quan- 
tity 
(cubic 

Value. 

Quan- 
tity 
(num- 
ber of 

Value. 

Value. 

value. 

blocks). 

Washington  and  Orange 
Windsor  

1,094,619 
12,000 

$1,015,006 
6,000 

164,706 

$576,551 

50,400 

$1,262 

$14,443 

$2,047,100 
309,904 

Caledonia  and  Orleans  . 

117,560 

66,580 

1,000 

5,666 

2,175 

77,754 

Windham  

11,750 

7,637 

200 

500 

7,800 

285 

716 

17  175 

Total  

1,235,929 

1,095,223 
.89 

165,906 

582,051 
3  51 

58,200 

1,547 

17,334 

2,451,933 

Average  price  per  cu.  ft. 

GRANITES  AND  OTHER  ACID  ROCKS 


67 


TABLE  34.  — PRODUCTION  OF  GRANITE  IN  VERMONT  IN 
1908  AND  1909,  BY  COUNTIES  AND  USES  (Concluded). 

1909. 


County. 

Number  of 
firms  re- 
porting. 

Building. 

Rough. 

Dressed. 

Quantity 
(cubic  feet). 

Value. 

Quantity 
(cubic  feet). 

Value. 

Washington  and  Orange  
Windsor 

34 
3 
10 
3 
3 

44,020 
111,020 
45,000 
12,950 
750 

$17,457    ) 
88,816    ) 
17,285 
4,550 
125 

381,730 
500 

$1,034,575 
500 

Caledonia  and  Essex  
Windham 

Orleans  

Total  
Average  price  per  cu.  ft  

53 

213,740 

128,233 
.60 

382,230 

1,035,075 
2.71 

Monumental. 

Other 

Paving. 

pur- 

Rough. 

Dressed. 

poses. 

County. 

Total 

Quan- 
tity (cu- 

Value. 

Quan- 
tity (cu- 

Value. 

Quan- 
tity 
(num- 

Value. 

Value. 

value. 

bic  feet). 

ber  of 

blocks) 

Washington  and  Orange  ) 
Windsor 

1,210,696 

$1,094,616 

173,242 

$478,349 

29,885 

$897 

$8,161  { 

$2,297,910 
424,961 

Caledonia  and  Essex  

94,962 

44,789 

62,574 

Windham  
Orleans  

233 
37,943 

233 

15,188 

100 
400 

250 
816 

134,000 

4,927 

110 
100 

10,070 
16,229 

Total  
Average  price  per  cu.  ft.  .  . 

1,343,834 

1,154,826 
.86 

173,742 

479,415 
2.76 

163,885 

5,824 

8,371 

2,811,744 

68  BUILDING  STONES  AND  CLAYS 

References  on  Granites.  —  The  following  list  contains  the  prin- 
cipal papers  and  reports  dealing  with  granites  and  allied  stones, 
chiefly  from  a  commercial  standpoint.  For  convenience  of 
reference,  the  titles  are  arranged  by  states,  in  alphabetical  order. 

Alabama: 

Watson,  T.  L.     Granites  of  the  southeastern  Atlantic  States.     Bull.  426, 

U.  S.  Geol.  Sur.,  1910.     Alabama  granites  on  pp.  268,  269. 
Arkansas: 

Williams,  J.  F.     The  igneous  rocks  of  Arkansas.     Vol.  II,  Ann.  Rep. 

Ark.  Geol.  Sur.  for  1890,  457  pp.     1891. 
California: 

Anon.     Granites  of  California.     Bull.  38,  Calif.  State  Mining  Bureau, 

pp.  23-61.     1906. 
Connecticut: 

Dale,  T.  N.     Granites  of  Connecticut.     Bull.  .  .  .  ,  U.  S.  Geol.  Sur.  (in 

press,  1911). 
Georgia: 

Watson,  T.  L.     Preliminary  report  on  the  granites  of  Georgia.     Bull.  9, 

Georgia  Geol.  Sur.,  367  pp.     1902. 
Watson,  T.  L.     Granites  of  the  southeastern  United  States.     Bull.  426, 

U.  S.  Geol.  Sur.,  1910.     Georgia  granites  on  pp.  206-267. 
Maine: 

Dale,  T.  N.     The  granites  of  Maine.     Bull.  313,  U.  S.  Geol.  Sur., 

202pp.    1907. 
Maryland: 

Grimsley,  G.  P.     The  granites  of  Cecil  County,  in  northeastern  Maryland. 

Jour.  Cinn.  Soc.  Nat.  Hist.,  Vol.  XVII,  pp.  59-67,  78-114.     1894. 
Keyes,  C.  R.     The  origin  and  relations  of  Central  Maryland  granites. 

15th  Ann.  Rep.  U.  S.  Geol.  Sur.,  pp.  685-740.     1895. 
Mathews,  E.  B.     Granites  and  gneisses  of  Maryland.     Vol.  II,  Rep.  Md. 

Geol.  Sur.,  pp.  136-169.     1898. 
Watson,  T.  L.     Granites  of  the  southeastern  United  States.     Bull.  426, 

U.  S.  Geol.  Sur.,  1910.     Maryland  granites  on  pp.  39-69. 
Williams,  G.  H.     Granitic  rocks  in  the  middle  Atlantic  piedmont  plateau. 

15th  Ann.  Rep.  U.  S.  Geol.  Sur.,  pp.  657-684.     1895. 
Massachusetts: 

Dale,  T.  N.    The  chief  commercial  granites  of  Massachusetts.     Bull.  354, 

U.  S.  Geol.  Sur.,  pp.  73-144.     1908. 
Minnesota: 

Winchell,   N.  H.     The  comparative  strength  of  Minnesota  and  New 
England  granites.     12th  Ann.  Rep.  Minn.  Geol.  Sur.,  pp.  14-18. 
1884. 
Missouri: 

Buehler,  H.  A.      Granites  and  rhyolites  of  Missouri.      Rep.  Mo.  Geol. 
Sur.,  2d  series,  Vol.  II,  pp.  60-85.     1904. 


GRANITES  AND  OTHER  ACID   ROCKS  69 

New  Hampshire: 

Dale,  T.  N.    The  chief  commercial  granites  of  New  Hampshire.    Bull. 
354,  U.  S.  Geol.  Sur.,  pp.  144-188.     1908. 

New  Jersey: 

Lewis,  J.  V.     Building  stones  of  New  Jersey.    Ann.  Rep.  State  Geologist 

N.  J.  for  1908.     Granite,  pp.  62-81.     1909. 
New  York: 

Eckel,  E.  C.     The  quarry  industry  in  southeastern  New  York.     20th 

Ann.  Rep.  N.  Y.  State  Geologist,  pp.  141-176.     1902. 
Smock,  J.  C.     Building  stones  in  the  State  of  New  York.    Bull.  3,  N.  Y. 

State  Museum,  152  pp.     1888. 
Smock,  J.  C.     Building  stone  in  New  York.     Bull.  10,  N.  Y.  State 

Museum,  396  pp.     1890. 
North  Carolina: 

Watson,  T.  L.     Granites  of  the  southeastern  United  States.    Bull.  426, 

U.  S.  Geol.  Sur.,  1910.     North  Carolina,  pp.  115-170. 
Rhode  Island: 

Dale,  T.  N.    The  chief  commercial  granites  of  Rhode  Island.     Bull.  354, 

U.  S.  Geol.  Sur.,  pp.  188-210.     1908. 
South  Carolina: 

Watson,  T.  L.     Granites  of  the  southeastern  United  States.     Bull.  426, 

U.  S.  Geol.  Sur.,  1910.    South  Carolina,  pp.  172-205. 
South  Dakota: 

Todd,  J.  E.    The  newly  discovered  rock  at  Sioux  Falls,  South  Dakota. 

Am.  Geologist,  Vol.  XXXIII,  pp.  35-39.     1904. 
Texas: 

Burchard,  E.  F.    Structural  materials  in  the  vicinity  of  Austin,  Texas. 

Bull.  430,  U.  S.  Geol.  Sur.,  pp.  292-316. 
Vermont: 

Dale,  T.  N.     The  granites  of  Vermont.     Bull.  404,  U.  S.  Geol.  Sur., 

138  pp.     1909. 
Finlay,  G.  I.    The  granite  area  of  Barre,  Vermont.    Rep.  Vt.  State 

Geologist  for  1901-1902,  pp.  46-59.     1902. 
Perkins,  G.  H.     Report  on  the  marble,  slate,  and  granite  industries  of 

Vermont,  68  pp.     Rutland,  1898. 
Perkins,  G.  H.     Granite  (in  Vermont).     Rep.  Vt.  State  Geologist  for 

1899-1900,  pp.  57-77.     1900. 
Virginia: 

Watson,  T.  L.    Granites  of  the  southeastern  United  States.     Bull.  426, 

U.  S.  Geol.  Sur.,  1910.     Virginia,  pp.  70-115. 
Washington: 

Landes,  H.    The  building  and  ornamental  stones  of  Washington.    Vol. 

II.     Rep.  Wash.  Geol.  Sur.,  1903.     Granites,  pp.  32-47. 
Wisconsin: 

Buckley,  E.  R.    Building  and  ornamental  stones  of  Wisconsin.     Bull.  4, 
Wis.  Geol.  Sur.,  500  pp.     1898. 


CHAPTER   IV. 
TRAP  ROCK  AND  OTHER  BASIC  IGNEOUS  STONES. 

Scope  of  Term.  —  The  term  trap  rock  is  applied  commercially 
to  a  series  of  basic  igneous  rocks  which  usually  agree  in  being 
dark-colored,  dense  and  fine-grained.  With  few  exceptions,  the 
commercial  trap  rocks  are  geologically  classified  as  either  basalt, 
diabase  or  gabbro.  Occasionally,  however,  some  of  the  finer- 
grained,  dark-colored  diorites  are  marketed  as  trap. 

For  convenience,  so  as  to  avoid  too  violent  a  separation  of 
geologically  allied  rocks,  all  of  the  more  basic  rocks  will  be  treated 
together  in  the  present  chapter.  The  groups  thus  covered  in- 
clude the  diorites,  gabbros,  diabase  and  basalt,  and  the  still  more 
basic  peridotites,  pyroxenites  and  hornblendites. 

Occurrence  of  Trap  Rocks.  —  The  general  modes  of  occurrence 
of  igneous  rocks  have  been  discussed  on  pages  17-20  of  this  vol- 
ume, but  in  the  present  place  it  will  be  well  to  consider,  in  some- 
what greater  detail,  such  phases  of  this  matter  as  bear  on  the 
occurrence  of  trap  rocks  in  particular. 

For  our  present  purpose  it  is  sufficiently  exact  to  say  that 
practically  all  of  the  basic  igneous  rocks  which  are  of  commercial 
importance  will  be  found  to  occur  in  one  of  the  following  types 
of  deposit: 

(1)  In  certain  regions  of  pre-Cambrian  rocks,  both  massive 
basic  rocks  and  basic  gneisses  are  found  to  cover  considerable 
areas.     Most  of  the  traps  of  Wisconsin,  Minnesota  and  Michigan 
are  of  this  type;  while  many  of  the  basic  gneisses  quarried  in  the 
eastern  states  are  also  from  pre-Cambrian  areas. 

(2)  The  bulk  of  the  commercial  trap  rock,  however,  comes 
from  deposits  which  are  of  more  recent  and  more  clearly  recog- 
nizable   origin.     In    Massachusetts,    Connecticut,    New    York, 
New  Jersey,  Pennsylvania  and  Virginia  the  trap  quarried  is  of 
Triassic  age,  and  comes  from  intrusive  sheets  or  surface  flows. 
More  rarely  quarries  of  trap  are  established  on  dikes  or  in  old 
volcanic  necks. 

70 


TRAP  ROCK  AND  OTHER  BASIC  IGNEOUS  STONES       71 

Color.  —  Owing  to  their  low  silica  content,  and  the  prevalence 
of  iron  minerals,  the  basic  igneous  rocks  are  commonly  dark 
colored.  In  the  coarser-grained  varieties  of  gabbro  and  diorite, 
the  color  effect  may  be  mottled,  the  dark  iron  minerals  being  set 
off  by  feldspars  which  are  lighter  in  tint,  though  in  the  basic  rocks 
even  the  feldspars  are  commonly  bluish  or  grayish.  In  the  finer- 
grained  diorites  and  gabbros,  and  in  the  basalts,  diabases  and  ul- 
trabasic  rocks  the  color  is  commonly  almost  uniform,  and  ranges 
from  dark  green  or  dark  gray  to  almost  black. 


Fig.  16.  —  Columnar  structure  of  trap.     (Photo  by  N.  H.  Darton.) 

The  above  notes  apply  to  the  colors  shown  by  these  rocks 
when  fresh.  As  all  the  basic  rocks  are  susceptible  to  weathering, 
old  outcrops  usually  show  very  different  colors  from  that  of  the 
fresh  rock.  On  such  weathered  surfaces  any  feldspar  which  the 
rock  may  contain  is  usually  a  dull  chalky  white;  while  the  iron- 
bearing  minerals  have  taken  on  yellowish,  reddish  or  brown 
tints. 

Mineral  Constitution.  —  In  none  of  the  basic  igneous  rocks  is 
quartz  an  important  constituent ;  and  in  most  of  them  it  is  either 
entirely  or  practically  lacking.  The  feldspar  of  the  basic  rocks 
is  usually  plagioclase,  and  not  orthoclase.  When  a  mica  is 


72 


BUILDING  STONES  AND  CLAYS 


present,  it  is  commonly  biotite,  and  not  muscovite.  All  of  the 
basic  rocks  contain  either  hornblende,  pyroxene  or  olivine;  and 
in  some  cases  very  large  amounts  of  one  or  more  of  these  very 
basic  minerals. 

The  proportions  of  the  various  minerals  present  in  a  number 
of  specimens  of  diabase  from  New  Jersey  has  been  determined 
by  Lewis  with  the  results  shown  in  the  following  table.  For 
convenience  of  comparison,  Lewis'  results  have  been  renumbered, 
so  as  to  correspond  with  the  numbers  given  to  the  chemical 
analyses  of  the  same  specimens  in  Table  38  on  a  later  page. 


TABLE  35.  —MINERAL  PROPORTIONS  IN  TRAP  ROCKS. 


l 

2 

6 

7 

8 

9 

10 

Quartz  

Per  cent 
19 

Per  cent 

7 

0 

o 

o 

o 

0 

Feldspar 

44 

42 

20 

38 

37 

QO 

26 

Augite 

27 

34 

73 

46 

59 

RQ 

56 

Biotite.  . 

3 

o 

1 

1 

o 

o 

1 

Olivine.  .    . 

0 

o 

4 

13 

1 

5 

16 

Magnetite,  etc  

7 

17 

2 

2 

3 

2 

1 

Identification  of  Constituents.  —  Except  in  dealing  with  very 
coarse-grained  types  it  will  rarely  be  possible  to  identify  the 
mineral  constituents  of  a  basic  rock  by  merely  examining  it  with 
the  naked  eye  or  even  with  a  hand  lens.  In  order  to  classify  the 
rock  correctly,  either  chemical  analysis  or  microscopic  investi- 
gation will  be  necessary,  and  frequently  both  will  be  required. 

Chemical  Composition.  —  The  rocks  included  in  this  group  are 
all  characteristically  low  in  silica,  and  relatively  high  in  iron 
oxide,  magnesia,  lime  and  alkalies. 

The  following  tables  (Tables  36-40)  contain  analyses  of  a 
representative  series  of  commercial  trap  rocks  from  various 
producing  localities  in  the  United  States.  With  these  have  been 
included  a  few  analyses  of  basic  rocks  from  localities  which  have 
not  yet  entered  the  producing  list,  but  which  may  reasonably  be 
expected  to  do  so  in  the  near  future. 


TRAP  ROCK  AND  OTHER  BASIC  IGNEOUS  STONES   73 


TABLE  36.  —  ANALYSES  OF  TRAP:  CONNECTICUT. 


i 

2 

3 

4       '] 

Silica  (SiO2)  

52.37 

50.26 

49.27 

49.29 

Alumina  (Al2Oa)  

15.06 

15.16 

15.87 

15.97 

Titanic  oxide  (TiO2) 

0  21 

Ferric  oxide  (Fe2Os) 

2.34) 

j    1.93 

1.88 

Ferrous  oxide  (FeO)  
Manganous  oxide  (MnO)  
Lime  (CaO)  
Magnesia  (MgO)  

9.82? 
0.32 
7.33 
5.38 

13.70 

0.48 
10.68 
5.49 

)  10.17 
0.35 
7.46 
5.90 

10.23 
0.40 
7.42 
6.07 

Potash  (K2O)  

0.92 

n.d. 

0.71 

0.69 

Soda  (Na2O) 

4.04 

n,d. 

3.45 

3.35 

Carbon  dioxide  (CO2)         

1.12 

1.17 

Water  above  100°  C.  ) 

2.24 

4.23 

3.92 

3.88 

Water  below  100°  C.  )  ' 

1.  Connecticut  Trap  Rock  Quarries    Company,  Meriden;    J.  H.  Pratt, 

analyst;  18th  Ann.  Rep.  U.  S.  Geol.  Sur.,  pt.  5. 

2.  Cooke  Trap  Rock  Company,  Plainville;  H.  Souther,  analyst;  20th  Ann. 

Rep.  U.  S.  Geol.  Sur.,  pt.  6,  p.  365. 

3.  4.  Tidewater  Trap  Rock  Company,  East  Haven;  G.  W.  Hawes,  analyst; 

Min.  Res.  U.  S.  for  1903. 


TABLE  37. —  TRAP:  MASSACHUSETTS  AND  MINNESOTA. 


l 

2 

3 

4 

5 

6 

Silica  

52.59 

46.11 

50.43 

35.83 

48  32 

48  51 

Alumina  

23.42 

17.20 

23.83 

) 

35  95 

13  79 

Ferric  oxide 

14  55 

12  07 

>48  45 

) 

Ferrous  oxide  

4.87 

J17.63 

1 

19.34 

Lime 

9  05 

10  96 

4  79 

9  35 

12  05 

8  34 

Magnesia. 

0.28 

4  24 

2  46 

3  12 

0  25 

4  81 

Potash  

0  34 

0  22 

0  19 

0  19 

Soda  

2  06 

1  66 

2  98 

1  67 

Water  

3.06 

1.  Monson,  Hampden  County,  Mass.;  Watertown  Arsenal,  analysts;  20th 

Ann.  Rep.  U.  S.  Geol.  Sur.,  pt.  6,  p.  405. 

2.  West  Roxbury,  Suffolk  County,  Mass.;  H.  P.  Williams,  analyst;  Min. 

Res.  U.  S.  for  1903,  pamphlet  ed.,  p.  119. 

3.  Duluth,  St.  Louis  County,  Minn.     Dodge.    Vol.  I,  Rep.  Minn.  Geol. 

Sur.,  p.  198. 

4.  Taylor's  Falls,  Chicago  County,  Minn.     Dodge.     Vol.  I,  Rep.  Minn. 

Geol.  Sur.,  p.  198. 


74 


BUILDING  STONES  AND   CLAYS 


5.  Beaver  Bay,  Lake  County,  Minn.     Dodge.     Vol.  I,  Rep.  Minn.  Geol. 

Sur.,  p.  198. 

6.  Tischer's  Creek,  St.  Louis  County,  Minn.     Dodge.     Vol.  I,  Rep.  Minn. 

Geol.  Sur.,  p.  198. 


TABLE  38.  —  ANALYSES  OF  TRAP  ROCKS:  NEW  JERSEY.* 


1 

2 

3 

4 

5 

6 

7 

8 

9 

10 

11 

12 

13 

SiO2  .  . 

60.05 

51.34 

53.13 

51.88 

50.40 

52.48 

49.62    51.141  51.03 

49.02 

46.78 

51.46 

50.34 

A1203.. 

11.88 

12.71 

13.75    14.53115.  60 

14.98 

10.51!   12.99    11.92 

10.14 

14.33 

13.98 

15.23 

IS?'.: 

3.22 
10.21 

2.65 
14.14 

1.07 
9.10 

1.35j  3.65 
9.14    6.30 

1.13 
9.25 

0.64 
12.02 

1.50 
9.14 

1.52 
10.85 

1.54 
10.46 

5.76 
9.27 

2.66 
8.92 

2.82 
11.17 

MgO.. 

0.85 

3.66 

8.57 

7.78    6.08      7.75 

15.98 

11.58    12.08 

17.25 

1.58 

7.59 

5.81 

CaO.. 

4.76 

7.44 

9.47 

9.98  10.41 

10.83 

7.86 

10.08 

9.22 

8.29 

5.26 

10.49 

9.61 

Na^O.. 

4.04 

2.43 

2.30 

2.06 

2.57 

1.87 

1.40 

1.72 

1.50 

1.59 

3.43) 

4*7K 

(2.93 

K2O 

2.10 

1.44 

1.04 

0.93 

0.62 

0.43 

0.55 

0.52 

0.39 

0.40 

1.75  j 

.  la 

11.02 

HjO+. 

0.66 

0.69) 

OQA 

(0.97 

1.67 

0.23 

0.49 

0.59 

0.54 

0.59 

0.10 

0.07 

H2O  —  . 

0.21 

0.18( 

.VU 

10.12 

1.02 

0.18 

0.38 

0.14 

0.17 

0.16 

0.33 

0.19 

TiO» 

1.74 

3.47 

1.35 

1.35 

1.30 

l.Oll     1.13 

0.93 

0.99 

1.44 

"i'.oe 

1.56 

s&; 

0.52 
0.28 

0.20 
0.36 

'6!  44 

0.14 
0.10 

0.16 
0.06 

0.13 
0.27 

0.16 
0.09 

0.06 
0.16 

0.08 
0.15 

0.11 
0.16 

0.36 
0.25 

0.17 

0.20 
0.14 

100.52 

100.71 

99.77 

100.33 

99.89 

100.83 

100.71 

100.75 

100.38 

100.70 

100.64 

101.08 

101.09 

Sp.  gr. 

2.872 

3.089 

2.96 

2.98 

2.89 

3.110 

3.118 

3.051 

3.122 

3.152 

2.968 

14 

15 

16 

17 

18 

19 

20 

21 

22 

SiO2... 
A12O. 

50.19 
14  65 

51.09 
14  23 

51.77 
14  59 

51.82 
14  18 

51.84 
15  11 

51.36 
16  25 

49.68 
14  02 

49.17 
13  80 

49.71 
13  66 

aeE 

MgO 

3.41 
6.96 

7  95 

2.56 
7.74 
7  56 

3.62 
6.90 
7  18 

0.57 
9.07 
8  39 

1.78 
8.31 

7  27 

2.14 

8.24 
7  97 

4.97 
9.52 
5  80 

4.90 
10.61 
5  04 

5.49 
9.51 
6  13 

CaO  
NajO 

9.33 
2  64 

10.35 
1  92 

7.79 
3  92 

8.60 
2  79 

10.47 
1  87 

10.27 
1  54 

v6.50 
3  49 

9.87 
2  21 

5.85 
4  51 

K2O  
H20+  
H20-  
TiO2  
P2O5 

0.75 
2.38 
0.66 
1.13 
0  18 

0.42 
1.01 
1.66 
1.30 
0  16 

0.64 
1.85 
0.46 
1.13 
0  18 

1.26 
1.40 
0.30 
1.17 
0  17 

0.34 
1.33 
0.56 
1.22 
0  13 

1.06 
1.33 

1.41 
1.89 
0.54 
1.39 
0  21 

0.54 
0.73 
1.04 
1.50 
0  24 

0.37 
2.66 
0.48 
1.53 
0  10 

MnO  

0.07 

0.25 

0.05 

0.13 

0.09 

0.09 

0.18 

0.07 

0.13 

Sp.  gr. 

100.30 
2  92 

100.25 
2  936 

100.08 
2  91 

99.85 
2  95 

10.32 
2  93 

100.28 

99.60 
2.949 

99.75 
2.997 

100.13 
2.91 

*  Ann.  Rep.  N.  J.  State  Geol.  for  1907,  pp.  120  et  seq.  contain  analyses  1-22  of  this  table. 

1.  Quartz  diabase,  Penn.  R.  R.  tunnel,  Homestead;  R.  B.  Gage,  analyst. 

2.  Quartz   diabase,  Penn.  R.  R.  cut,  near  Marion  Station,  Jersey  City; 

R.  B.  Gage,  analyst. 

3.  Diabase,  Railroad  cut,  Jersey  City;  G.  W.  Hawes,  analyst. 

4.  Diabase,  Penn.  R.  R.  tunnels,  Weehawken;  R.  B.  Gage,  analyst. 

5.  Diabase,  N.  Y.,  Susquehanna  &  Western  R.  R.  tunnel;  R.  B.  Gage, 

analyst. 

6.  Diabase,  road  to  West  Shore  Ferry,  Weehawken;  R.  B.  Gage,  analyst. 


TRAP  ROCK  AND  OTHER  BASIC  IGNEOUS  STONES       75 

7.  Olivine   diabase,    second    road    to   West   Shore   Ferry,    Weehawken; 

R.  B.  Gage,  analyst. 

8,  9.   Diabase,  Englewood  Cliffs;  R.  B.  Gage,  analyst. 

10.  Olivine  diabase,  Englewood  Cliffs;  R.  B.  Gage,  analyst. 

11,  12,  13.   Diabase,   quarry  near    Rocky  Hill    station;   A.   H.   Phillips, 

analyst. 

14.  Hartshorn's  quarry,  near  Springfield  and  Short  Hills,  lower  "  gray  " 

layer;  R.  B.  Gage,  analyst. 

15.  Same  locality,  middle  "  black  "  layer;  R.  B.  Gage,  analyst. 

16.  Same  locality,  upper  "  gray  "  layer;  R.  B.  Gage,  analyst. 

17.  Hatfield  &  Weldon's    quarry,  Scotch    Plains,   lower  "  gray "    layer; 

R.  B.  Gage,  analyst. 

18.  Same  locality,  "  black  "  rock  above;  R.  B.  Gage,  analyst. 

19.  O'Rourke's  quarry,  West  Orange.     Large  columns  near  the  bottom. 

(Bull.  U.  S.  Geol.  Sur.,  No.  150,  p.  255);  L.  G.  Eakins,  analyst. 

20.  Morris    County    Crushed    Stone    Go's,     quarry,    Millington,    lower 

"  gray  "  layer;  R.  B.  Gage,  analyst. 

21.  Same  locality,  middle  "  black  "  layer;  R.  B.  Gage,  analyst. 

22.  Same  locality,  upper  "  gray  "  layer;  R.  B.  Gage,  analyst. 


The  following  table  contains  a  number  of  less  complete  com- 
mercial analyses  of  trap  rock  from  various  localities  in  New  Jersey. 

TABLE  38A.  —  TRAP:  NEW  JERSEY. 


23 

24 

25 

26 

27 

Silica 

50  81 

50  61 

49  20 

50  03 

51  20 

Alumina 

13  25 

18.34 

14.50 

18.20 

20  88 

Ferric  oxide     ) 

14  66 

13.91 

17.01 

16.81 

11  12 

Ferrous  oxide  ) 
Lime 

10  96 

7.01 

7.50 

11.10 

12  50 

Magnesia.    . 

6.97 

6.73 

6.30 

1.02 

2  17 

Potash  

1.71 

1.08  ) 

Soda  

0.76 

1.60) 

1.69 

1.03 

1.03 

Water  

0.88 

1.72 

3.80 

1.81 

1.10 

23.  Little  Falls,  Passaic  County;  W.  C.  Day,  analyst;  20th  Ann.  Rep. 

U.  S.  Geol.  Sur.,  pt.  6,  p.  419. 

24.  Mine  Brook,  Somerset  County;  T.  B.  Stillman,  analyst;  20th  Ann. 

Rep.  U.  S.  Geol.  Sur.,  pt.  6,  p.  419. 

25.  Millington',  Morris  County;  T.  B.  Stillman,  analyst;  20th  Ann.  Rep. 

U.  S.  Geol.  Sur.,  pt.  6,  p.  419. 

26.  Millingtonj,  Morris  County;  T.  B.  Stillman,  analyst;  20th  Ann.  Rep. 

U.  S.  Geol.  Sur.,  pt.  6,  p.  419. 

27.  Millington,  Morris  County;  T.  B.  Stillman,  analyst;  20th  Ann.  Rep. 

U.  S.  Geol.  Sur.,  pt.  6,  p.  419. 


76 


BUILDING  STONES  AND   CLAYS 


TABLE  39. —  ANALYSES  OF  GABBRO:   NEW  YORK. 


i 

2 

Silica  (SiO2) 

54  72 

55  34 

Alumina  (A^Oa)  . 

17  79 

16  37 

Ferric  oxide  (Fe2Os)  

2  08 

0  77 

Ferrous  oxide  (FeO)  

6  03 

7  54 

Lime  (CaO) 

6  84 

7  51 

Magnesia  (MgO).    . 

5  85 

5  05 

Potash  (K2O)  

3  01 

2  03 

Soda  (Na2O)  

3  02 

4  06 

Water  

0  58 

1.  Quaker  Bridge,  N.  Y.;  H.  T.  Vulte,  analyst;  "  Handbook  of  Rocks,"  3d 

ed.,  p.  72. 

2.  Montrose,  N.  Y.;  Dunn,  analyst;  "Handbook  of  Rocks,"  3d  ed.,  p.  72. 


TABLE  40. —  ANALYSES  OF  TRAP  ROCK:   PENNSYLVANIA 
AND  VIRGINIA. 


1 

2 

3 

4 

5 

6 

7 

Silica  
Alumina  
Ferric  oxide  
Ferrous  oxide  

46.87 
13.36 
9.79 
2.71 

52.65 
17.02 
4.61 

45.73 
13.48 
11.60 

47.87 
14.43 
11.55 

52.06 
13.67 
15.97 

51.31 
13.64 
0.52 

50.88 
13.17 
1.11 

Lime  

14  70 

6  35 

9  92 

10  45 

8  15 

12  41 

10  19 

Magnesia  

4  35 

2  87 

15  40 

10  58 

5  01 

12  73 

13  05 

Potash  
Soda 

2.01 
4  64 

1  7-42i 

0.47 
3  24 

0.61 
3  47 

0.86 
3  36 

0.32 
1  40 

0.31 
1  17 

Carbon  dioxide 

1    «  ™ 

Water  

>   9.03 

0.94 

1.82 

1.05 

0.14 

1.  Birdsboro,  Berks  County,  Pa.;  H.  Fleck,  analyst;  20th  Ann.  Rep.  U.  S. 

Geol.  Sur.,  pt.  6,  p.  435. 

2.  Rushland,  Bucks  Co.,  Pa.;  Lathbury  &  Spackman,  Analysts;  Min.  Res. 

U.  S.,  1903,  p.  155. 
3-5.   Chatham,  Pittsylvania  County,  Va.;  T.  L.  Watson,  analyst;  Min.  Res. 

of  Virginia,  1907,  p.  37. 
6-7.   North  of  Rapidan  Station,  Va.;  T.  L.  Watson,  analyst;  Min.  Res.  of 

Virginia,  1907,  p.  39. 

Physical  Properties.  —  Since  the  basic  rocks  are  not  ordina- 
rily attractive  in  color,  there  is  little  reason  to  quarry  them  unless 
they  are  entirely  sound  from  a  structural  point  of  view.  Com- 


TRAP  ROCK  AND  OTHER  BASIC  IGNEOUS  STONES       77 


paratively  few  tests  of  the  physical  properties  of  basic  stone  are 
on  record,  but  from  those  available  it  is  obvious  that  in  both 
strength  and  density  they  outrank  the  granites  and  other  acid 
rocks. 

TABLE  41.  —  PHYSICAL  PROPERTIES  OF   AMERICAN  TRAP 

ROCKS. 


State. 

Location. 

Tested  by 

Specific 
gravity. 

Weight  per 
cubic  foot. 

Compressive 

strength,  pounds  per 
square  inch. 

Min. 

Aver. 

Max. 

Connecticut                    

New  Haven  .... 
New  Haven  .... 
Meriden 

Gillmore  
Hawes  

2.60 
2.86 
2.965 

3.10 

2.802 
2.80 
3.005 
3.000 
2.704 

3.03 
2.96 

2  928 

162.5 

175.1 
175.0 

i87!5 
169.0 

189.5 

14,161 

9.500 
18.801 

27.250 
17.631 

'26!  250 
20.750 

21.500 
'24:046 
20.250 

21.035 

Maine 

Watertown  

Gillmore  
Gillmore  
Gillmore  
Gillmore  
Gillmore  

Gillmore  
Hawes  
Gillmore  

J.  S.  Newberry. 

West  Roxbury.. 

Duluth  
Duluth  
Tischer's  Creek 
Taylor's  Falls.  . 
Beaver  Bay  .... 

Jersey  City  
Jersey  City  
Pompton  

Cortland  Point. 
Quaker  Bridge  . 

Rushland  

Chatham  

Goose  Creek.  .  .  . 
Hapidan 

Minnesota 

New  Jersey  
New  York 

2.65 

2.953 
3.026 

3  095 

164.4 

Virginia  

Watson  { 

Watertown  
Watson 

23.000 

Uses  of  Trap  Rock.  —  The  basic  igneous  rocks  included  in  this 
group  could  of  course  be  used  as  building  stone,  or  for  any  of  the 
other  structural  uses  to  which  granites  are  applied,  but  as  a  mat- 
ter of  fact  they  are  rarely  so  used.  This  lack  of  use  for  these 
purposes  is  due  in  part  to  the  dark  and  somber  colors  usually 
characteristic  of  the  basic  stones;  and  also,  in  part,  to  their 
great  toughness  and  the  consequent  difficulty  and  expense  of 
dressing  them  for  structural  uses.  Added  to  these  disadvan- 
tages is  the  tendency,  shown  by  many  of  the  denser  basic  rocks, 
to  break  on  blasting  into  masses  whose  size  and  shape  render 
them  unfit  for  use  as  dimension  stone. 

On  the  other  hand,  the  very  features  which  render  the  traps 
generally  unserviceable  for  structural  purposes  are  of  advantage 


78 


BUILDING   STONES  AND  CLAYS 


for  other  uses.  In  consequence,  trap  rock  and  allied  stones  are 
largely  used  as  paving  blocks  and,  in  the  form  of  crushed  stone, 
as  road  metal,  railway  ballast  and  concrete  aggregate.  For  all 
of  these  purposes  darkness  of  color  is  of  no  disadvantage,  while 
density,  strength  and  toughness  are  of  direct  service. 

Production  of  Trap  Rock  in  the  United  States.  —  Complete 
statistics  covering  the  trap-rock  production  of  the  entire  United 
States  are  unfortunately  not  available.  This  condition  is  due 
to  the  fact  that  in  the  statistical  reports  on  the  stone  industry 
published  annually  by  the  United  States  Geological  Survey  the 
production  of  trap  is,  in  most  of  the  states,  included  with  that  of 
granite. 

The  trap-rock  production  of  the  six  most  important  producing 
states  is,  however,  reported  separately  by  the  Geological  Survey, 
and  these  partial  statistics  are  quoted  in  the  series  of  tables  which 
follow. 


TABLE  42.  —  TRAP-ROCK  PRODUCTION  OF  THE  UNITED 
STATES,  1899-1909. 


Year. 

Value. 

Year. 

Value. 

1899 

$1,275,041 

1905 

$3,074,554 

1900 

1,706,200 

1906 

3,736,571 

1901 

1,710,857 

1907 

4,594,103 

1902 

2,181,157 

1908 

4,282,406 

1903 

2,732,294 

1909 

5,133,842 

1904 

2,823,546 

1910 

6,452,121 

The  totals  given  in  the  preceding  table,  as  in  those  which 
follow,  cover  the  production  of  trap  rock  hi  the  states  of  Cali- 
fornia, Connecticut,  Massachusetts,  New  Jersey,  New  York  and 
Pennsylvania  only.  In  addition  to  this,  trap  rock  is  quarried 
more  or  less  steadily  in  Maine,  Minnesota,  Virginia,  Oregon  and 
Washington,  but  no  exact  data  on  the  output  of  these  states  are 
available. 


TRAP  ROCK  AND  OTHER  BASIC  IGNEOUS   STONES       79 


TABLE  43.  —  TRAP-ROCK  PRODUCTION  BY  STATES  AND 

USES,   1908-1909. 


1908. 


State. 

Building. 

Paving. 

Crushed  stone. 

Other. 

Total. 

Road- 
making. 

Railroad 
ballast. 

Concrete. 

California 

$722 
7,594 
12,235 
11,399 

8',593 

$114,996 
8,125 

"58^69 

"2',835 

$423,798 
199,540 
348,108 
578,570 
567,908 
195,769 

$148,154 
100,000 
30,695 
182,355 
20,580 
201,091 

$285,380 
152,950 
117,134 
235,967 
107,234 
106,987 

$6,089 

5,010 
500 
13,054 
28,231 
2,634 

$979,139 
473,219 
508,672 
1,079,514 
723,953 
517,909 

Connecticut.  .  .  . 
Massachusetts  . 
New  Jersey.  .  .  . 
New  York  
Pennsylvania  .  . 

Total  

40,543 

184,125 

2,313,693 

682,875 

1,005,652 

55,518 

4,282,406 

1909. 


State. 

Build- 
ing. 

Paving. 

Crushed  stone. 

Other. 

Total. 

Road- 
making. 

Rail- 
road 
ballast. 

Concrete. 

California  
Connecticut.  .  . 
Massachusetts. 
New  Jersey  .  .  . 
New  York  .... 

$900 
6,827 
13,250 
1,496 

$129,764 
2,720 

$799,846 
292,451 
337,839 
664,571 
662,448 
281,467 

$71,108 

28,905 
75,031 
138,134 
27,620 
259,241 

$361,255 
33,369 
247,382 
232,262 
70,708 
165,449 

$108,212 
3,383 

"il',729 
l',240 

$1,471,085 
367,655 
673,502 
1,140,571 
760,776 
720,253 

92,379 

Pennsylvania.  . 
Total  

11,056 

1,800 

33,529 

226,663 

3,038,622 

600,039 

1,110,425 

124,564 

5,133,842 

TABLE  44.  —  PRODUCTION   AND   VALUE   OF   TRAP   PAVING 
BLOCKS,  1908-1909. 


Paving  blocks. 


State. 

19( 

)8. 

19 

09. 

Number. 

Value. 

Number. 

Value. 

California. 

2  765  587 

$114  996 

3  060  078 

$129,764 

Connecticut  

232  160 

8  125 

80,590 

2,720 

New  Jersey  

1,665,983 

58  169 

2,105,720 

92,379 

Pennsylvania  

63,000 

2,835 

50,000 

1,800 

Total 

4  726  730 

184  125 

5  296  388 

226  663 

Average  price  per  thousand  

38.95 

42.80 

80  BUILDING  STONES  AND  CLAYS 

List  of  References  on  Trap  Rock.  —  The  following  list  con- 
tains the  titles  of  a  number  of  papers  and  reports  dealing  in  one 
way  or  another  with  this  subject.  Many  of  the  papers  cited  are 
primarily  geological  in  their  nature,  and  the  list  could  have  been 
greatly  extended  had  more  of  this  type  been  included. 

California: 

Anon.     Trap  rock  in  California.     Bull.  38,  Calif.  State  Mining  Bureau, 

pp.  56-61,  154-164.     1906. 
Connecticut: 

Davis,  W.  M.     The  quarries  in  the  lava  beds  at  Meriden,  Connecticut. 

Amer.  Jour.  Science,  4th  series,  Vol.  I,  pp.  1-13.     1896. 
Davis,  W.  M.     The  Triassic  formations  of  Connecticut.     18th  Ann.  Rep. 

U.  S.  Geol.  Sur.,  pt.  2,  pp.  9-192.     1898. 
Georgia: 

MeCaltie,  S.  W.     Roads  and  road-building  materials  of  Georgia.     Bull.  8, 

Georgia  Geol.  Sur.,  1901. 
New  Jersey: 

Lewis,  J.  V.     The  origin  and  relations  of  the  Newark  rocks.     Ann.  Rep. 

State  Geol.  N.  J.  for  1906,  pp.  99-130.     1907. 
Lewis,  J.  V.     Properties  of  trap  rocks  for  road  construction.     Ann.  Rep. 

State  Geol.  N.  J.  for  1906,  pp.  165-172.     1907. 
Lewis,  J.  V.     Petrography  of  the  Newark  igneous  rocks  of  New  Jersey. 

Ann.  Rep.  State  Geol.  N.  J.  for  1907,  pp.  97-168.     1908. 
Lewis,  J.  V.     Building  stones  of  New  Jersey.     Ann.  Rep.  State  Geol. 

N.  J.  for  1908,  pp.  81-83,  trap.     1909. 
New  York: 

Eckel,  E.  C.     The  quarry  industry  in  southeastern  New  York.     20th 

Ann.  Rep.  N.  Y.  State  Museum,  pp.  141-176.     1902. 
Newberry,  S.  B.     Kersantite  —  a  new  building  stone.     School  of  Mines 

Quarterly,  Vol.  VIII,  pp.  330-333.     1887. 
Smock,  J.  C.     Building  Stone  in  New  York.     Bulletins  3  and  10,  N.  Y. 

State  Museum. 
Virginia: 

Watson,  T.  L.     Mineral  Resources  of  Virginia,  1907,  pp.  36-41,  trap. 


CHAPTER  V. 


SERPENTINE   AND   SOAPSTONE. 

Relation  of  Serpentine  and  Soapstone.  —  Two  classes  of  rocks 
—  serpentines  and  soapstones  —  will,  for  convenience,  be  con- 
sidered together  in  the  present  chapter.  The  two  classes  have, 
in  fact,  many  points  of  resemblance  so  far  as  origin  and  character 
are  concerned;  though  industrially  they  are  often  applied  to 
widely  different  uses. 

Both  serpentine  and  soapstone  are  hydrous  magnesian  silicates; 
and  both  have  originated  through  the  hydration  of  basic  silicate 
rocks  or  minerals.  Neither  serpentine  nor  soapstone  is  there- 
fore directly  igneous  in  origin,  but  rather  a  secondary  result  of 
the  alteration  of  an  igneous  (or  metamorphic)  rock  or  mineral. 
Their  close  relationship  chemically,  as  well  as  their  principal 
points  of  difference,  are  well  brought  out  when  their  analyses* 
are  compared,  as  below. 


Silica. 

Magnesia. 

Water. 

Serpentine 

Per  cent. 
44   14 

Per  cent. 
42  97 

Per  cent. 
12  89 

Soapstone  (talc)  

62.00 

33.10 

4.90 

On  comparison  of  these  analyses  it  will  be  seen  that  both  of  the 
rocks  under  consideration  are,  when  theoretically  pure,  hydrous 
silicates  of  magnesia;-  and  that  they  differ  only  in  the  relative 
proportions  of  their  three  essential  constituents  —  silica,  mag- 
nesia and  combined  water. 

In  the  following  sections  of  this  chapter,  the  origin  and  charac- 
ters of  serpentine  will  first  be  discussed,  after  which  a  brief  con- 
sideration will  be  given  to  the  soapstones  and  allied  products. 

SERPENTINE. 

Serpentine,  Ophicalcite,  and  Ophimagnesite.  —  The  term  ser- 
pentine is  applied  to  a  series  of  soft  greenish  rocks  composed 
largely  or  entirely  of  the  mineral  serpentine,  which,  in  turn,  is  a 
*  Quoted  from  Kemp's  "  Handbook  of  Rocks,"  3d  ed.,  pp.  140,  141. 

81 


82  BUILDING  STONES  AND  CLAYS 

hydrous  silicate  of  magnesia.  The  term  ophicalcite  is  applied 
to  crystalline  marbles  containing  disseminated  seams,  streaks, 
or  masses  of  the  mineral  serpentine.  The  term  ophimagnesite, 
used  in  this  volume  for  the  first  time,  is  suggested  to  cover  the 
common  but  rarely  recognized  phase  in  which  the  rock  is  crys- 
talline magnesite,  containing  disseminated  serpentine. 

Origin  of  Serpentines.  —  Though  serpentine  is  not  strictly 
speaking  an  igneous  rock  most  large  serpentine  deposits  have 
been  derived  from  the  alteration  in  place  of  basic  igneous  rocks. 
A  few  deposits  (including  the  ophicalcites)  owe  their  origin  to  a 
less  direct  process,  involving  the  metamorphism  and  crystalliza- 
tion of  an  impure  limestone,  and  the  subsequent  alteration  of  the 
magnesian  silicate  minerals  developed  in  the  crystalline  marble. 
These  two  methods  of  origin,  which  differ  somewhat  in  results  as 
well  as  in  process,  will  be  briefly  described  below;  while,  for  a 
more  complete  discussion  of  the  subject  reference  should  be  made 
to  the  papers  cited  in  the  list  on  page  87,  and  particularly  to 
those  by  F.  J.  H.  Merrill  and  G.  P.  Merrill. 

(1)  Though  other  methods  of  origin  have  at  times  been  sug- 
gested, it  may  be  taken  as  proven  that  the  bulk  of  the  larger  and 
purer  deposits  of  serpentine  everywhere  have  originated  from  the 
alteration  (hydration)  of  basic  igneous  rocks,  rich  in  magnesian 
silicate  minerals.     The  particular  minerals  which  appear  to  be 
the  commonest  source  of  serpentine  are  olivine,  pyroxene,  and 
hornblende. 

All  of  the  minerals  named  are  more  or  less  basic  silicates  of 
magnesia  and  iron.  When  subjected  to  surface  weathering,  or 
to  the  continued  action  of  waters  at  or  near  the  surface,  they 
are  decomposed  with  the  formation  of  hydrated  magnesium  sili- 
cates and  iron  oxide.  Among  the  hydrated  silicates  so  formed, 
serpentine  is  commonly  the  most  abundant. 

(2)  A  second  class  of  serpentine  deposits,  much  less  common 
though  still  of  considerable  commercial  importance,  originate  in 
a  way  differing  slightly  in  detail  from  that  last  discussed.     This 
class  includes  the  ophicalcites,  in  which  serpentine  masses,  seams, 
or  stringers  are  scattered  through  a  ground  mass  of  crystalline 
marble.     In  this  case,  the  process  of  origin  appears  to  have  in- 
cluded several  steps.     In  the  first  place,  an  impure  limestone, 
carrying  considerable  silica,  was  metamorphosed  so  as  to  become 
thoroughly  crystalline.      During  this  change,  the  impurities  of 


SERPENTINE  AND   SOAPSTONE 


83 


the  limestone,  with  possibly  some  additional  matter  from  other 
sources,  crystallized  out  separately  in  the  form  of  various  sili- 
cate minerals;  so  that  the  result  of  the  metamorphism  was  the 
production  of  a  crystalline  marble  through  which  were  scattered 
crystals  of  hornblende,  pyroxene  and  other  silicate  minerals. 
Later,  these  silicates  were  hydrated  to  serpentine,  so  that  an 
ophicalcite  was  produced. 

Chemical  Composition  of  Serpentine.  —  Though  the  chemical 
composition  of  the  mineral  serpentine  is  definite  enough,  wide 
variations  in  composition  are  shown  by  stones  which  are  grouped 
commercially  under  the  same  name. 

The  two  tables  which  follow  contain  a  number  of  analyses  of 
normal  serpentines,  of  ophicalcites  and  of  ophimagnesites  from 
various  American  localities. 

TABLE  45.  —  ANALYSES  OF  SERPENTINES. 


1 

2 

3 

28.80 
5.54 

Yeo 

4.75 
0.33 

34.  41 

4  * 

5* 

40.06 
1.37 
3.02 

'3:43 
0.20 

39.02 

6t 

7 

8 

45.02 
3.35 

37  '.75 

{::: 

9 
41.55 

10 

11 

Silica  (SiO2) 

39.48 

34.84 
0.42 

Y'eios 

i    1.85 
0.68 
7.02 
30.74 
0.07 

43.87 
0.31 

'i'.ii 
'6^62 

38.62 

40.39 
1.01 
6.22 

'6:<J7 

tr. 
38.32 

43.72 
16.86 

tr. 

'Y22 
23.78 

J2.30 

42.60 

43.30 

Alumina  (A12O3)  

Magnetic  oxide  (Fe3O4)  
Ferric  oxide  (Fe2O3)    ) 
Ferrous  oxide  (FeO)    )  "  ' 
Chromium  oxide  (Cr2O3) 

20.18 

3.90 
40'i5 

8  30 

6  60 
35  50 

5^32 
39^55 

Lime  (CaO)  
Magnesia  (MgO)  
Potash  (K2O)  

37.74 

Soda  (Na2O)  
Carbon  dioxide  (CO2) 

0.42 
J17.39 

20.75 

^55 

ii.79 

Water  

1.69 

12.10 

12.86 

ii.io 

13.01 

13.70 

13.00 

*  Nickel  oxide,  NiO,  0.71.        t  Nickel  oxide,  0.23. 

1.  Auburn,  Placer  County,  Calif.;  B.  S.  Stone,  analyst;  Min.  Res.  U.  S. 

1903. 

2.  Monte  Diablo,  Calif.;  Kemp's  "  Handbook  of  Rocks,"  3d  ed.,  p.  140. 

3.  Holly  Springs,  Cherokee  County,  Ga.;  Mariner  and  Hoskins,  analysts; 

letter  to  author,  1904. 

4.  Webster,  N.  C.;  F.  A.  Genth,  analyst;  Kemp's  "Handbook  of  Rocks," 

p.  140. 

5.  6.   Broad  Creek,  Harford  County,  Md.;  F.  A.  Genth,  analyst;  Vol.  II, 

Rept.  Md.  Geol.  Sur.,  p.  195. 

7.  Near  Silver  City,  New  Mexico;  Merrill,  "Stone  for  Building  and  Deco- 

ration," p.  366. 

8.  Lancaster  County,  Pa.;  F.  A.  Genth,  analyst;  "  Mineralogy  of  Pennsyl- 

vania," p.  116. 

9.  Easton,  Pa.;  F.  A.  Genth,  analyst;   "  Mineralogy  of  Pennsylvania," 

p.  116. 

10.  Roxbury,  Vt.;  Geology  of  Vermont,  Vol.  II,  p.  779. 

11.  Cavendish,  Vt.;  Geology  of  Vermont,  Vol.  II,  779. 


84 


BUILDING  STONES  AND  CLAYS 


Regarding  the  analyses  presented  in  the  foregoing  table 
(Table  45),  it  may  be  noted  that  analysis  No.  1  is  difficult  to 
understand,  even  after  allowing  for  the  fact  that  the  chemist 
reported  it  on  a  practically  water-free  bjasis.  Analysis  No.  3, 
of  serpentine  from  Holly  Springs,  Georgia,  was  probably  made  on 
a  badly  selected  sample,  containing  much  more  lime  carbonate 
than  is  ordinarily  carried  by  the  stone  from  that  quarry,  which 
is  really  a  very  good  serpentine  and  not  an  ophicalcite,  as  might 
be  inferred  from  the  analysis  published. 

In  the  following  table  are  presented  the  results  of  analyses  of 
serpentines  and  allied  products  from  the  state  of  Washington. 
This  group  of  analyses  is  of  peculiar  interest  both  geologically 
and  chemically,  a  fact  which  apparently  escaped  attention  in  its 
first  publication.  For  convenience,  the  analyses  have  been 
arranged  in  an  order  which  brings  out  the  peculiarities  of  these 
Washington  rocks,  all  of  which  were  originally  described  as  mar- 
bles. It  will  be  seen  that  No.  1  is  a  true  serpentine;  that  Nos. 
2,  3,  4  and  5  are  serpentinous  limestones  (ophicalcites  or  ophi- 
dolomites);  that  Nos.  6  and  7  are  very  pure  magnesites;  and  that 
Nos.  8  and  9  are  serpentinous  magnesites  or  ophimagnesites. 

TABLE  46.  —  ANALYSES  OF  SERPENTINES  AND  ALLIED 
ROCKS,   WASHINGTON  STATE. 


i 

2 

3 

4 

5 

6 

7 

8 

9 

Silica  

38.47 
0.16 
2.04 
tr. 

40.35 

'i!66 
11.85 
22.07 
17.22 
6.85 

27.93 
2.32 
2.08 
2.38 
13.05 
27.74 
11.33 
13.17 

27.11 
1.90 
2.44 
1.80 
23.68 
15.45 
19.30 
8.32 

18.18 
0.44 
0.45 
1.17 
24.74 
16.10 
38.18 
0.74 

0.89 

6!58 

45.76 
49.24 
3.53 

5.79 
0.43 
0.85 

'i'69 
42.07 
47.23 
1.94 

15.30 
3.00 
3.32 
tr. 

52^89 
1.27 
24.22 

13.08 
1.63 
1.25 
0.19 
0.33 
56.44 
2.03 
24.79 

Alumina  
Ferric  oxide  
Ferrous  oxide  
Lime 

Magnesia  
Carbon  dioxide  

39.86 
4.84 
14.63 

Water 

Of  the  above  analyses,  Nos.  1  to  8  inclusive  were  made  by 
R.  W.  Thatcher;  No.  8  is  by  George  Steiger.  All  are  quoted  from 
Vol.  II,  Reports  Washington  State  Geological  Survey,  pages  91 
and  141.  The  localities  are  as  follows: 

1,  2.   North  American  Marble  Company,  Valley,  Stevens  County. 

3.  Spokane  Marble  Company,  Milan. 

4.  Pacific  Coast  Marble  Company,  Valley. 

5.  Washington  State  Marble  Company,  Valley. 

6.  7,  8,  9.   United  States  Marble  Company,  Valley. 


SERPENTINE  AND  SOAPSTONE 


85 


Defects  of  Serpentine.  —  Though  serpentine  is  of  quite  common 
occurrence  in  the  regions  of  metamorphic  and  igneous  rocks,  work- 
able deposits  are  rare,  owing  to  certain  defects  which  are  apt  to 
occur  in  this  stone.  These  defects  are  directly  traceable  to  the 
method  by  which  serpentine  has  been  formed,  and  therefore  can- 
not be  avoided  or  remedied  by  the  quarryman.  The  principal 
common  defect  is  that  the  mass  of  serpentine  is  so  cut  up  by 
cracks  and  joints  that  no  good-sized  blocks  can  be  obtained. 
The  other  frequent  defect  is  that  the  serpentine  is  apt  to  contain 
little  hard  crystals  of  pyrite,  chromite  or  magnetite.  These  inter- 
fere with  the  production  of  polished  slabs  for  interior  decoration, 
while  the  pyrite  has  the  further  evil  effect  of  decomposing  on 
exposure  to  the  atmosphere  and  leaving  a  yellow-brown  blotch 
of  iron  oxide. 

Physical  Properties  of  Serpentines.  —  Because  of  the  structure 
of  serpentines,  the  results  of  physical  tests  are  of  even  less  value 
than  with  other  structural  stones.  There  is  no  difficulty  in 
getting  out  a  small  cube  of  serpentine  which  will  show  good 
results  in  the  testing  machine;  but  that  is  about  as  far  as  the 
matter  goes. 

In  Table  48  the  results  of  a  number  of  tests  of  American  ser- 
pentines of  all  types  are  quoted.  For  convenience,  these  have 
been  averaged  and  compared,  in  the  table  immediately  following 
this  paragraph,  with  certain  German  tests  reported  by  Kriiger. 


TABLE  47.  —  AVERAGE  PHYSICAL  PROPERTIES  OF  SER- 
PENTINES. 


Specific  gravity. 

Weight 
per  cu- 
bic foot 

Compressive  strength,  pounds 
per  square  inch. 

Mini- 
mum. 

Aver- 
age. 

Maxi- 
mum. 

Aver- 
age. 

Mini- 
mum. 

Average. 

Maximum. 

American  tests  
German  tests  

2.545 
2.560 

2.727 
2.727 

2.908 

2.894 

170.2 
170.2 

8.950 

11.287 
11.950 

14.820 

The  close  coincidence  in  results  of  the  two  series  of  tests  is  an 
interesting  accident,  and  should  not  be  given  too  much  impor- 
tance. 


86 


BUILDING  STONES  AND  CLAYS 


TABLE  48.  —  PHYSICAL  PROPERTIES  OF  AMERICAN 
SERPENTINES. 


State. 

Location. 

1. 

££ 
|. 

% 

Weight  per 
cubic  foot. 

Absorption, 
per  cent. 

Compression  tests. 

. 
Tested  by 

"o® 

s| 

88* 

•Srf 
o  1 

X* 

•sa 

si 

<J 

II 

California 
Maryland 

Texas 
Wash. 

Germany 

Auburn  

Broad  Creek.... 
Broad  Creek  

2.545 

2.668 
2.669 

159.1 

In. 
1* 

3 

11,590 

GillespieCo  

Milan,  dark  
Milan,  light  yel- 

VaSeyi'  black".'.'. 
Blue,  Col  ville.... 
White     and    yel- 
low, Colville.  .  . 
White,  Colville.. 
White,      Chewe- 
lah  

2.61 

159.7 

0.0079 

2 

2 
2 

1 
3 

3 
2 

8,210 

12,180 
27,800 

8,950 
9,520 

13,530 
29,750 

10,400 

14,820 
31,700 

Univ.  of  Texas 

2'.908" 
2.594 

2.720 
2.719 

2.754 
2.858 
2.696 

2:874" 
2.73 
2.829 

2.56    ) 
2.894  } 

18Q.3 
161.2 

167.2 
166.6 

170.2 
177.4 
166.3 

178^8 
169.1 
173.8 

0.14 
0.07 

0.12 
0.35 

0.15 
0.17 
0.33 

o'.os" 

0.24 
1.32 

0.56J 

23,110 

Valley,  pink  and 
white  
Milan,  white  and 
green  
Valley,  green  
Valley,  green  
Dhewelah  
Bossburg  
Valley,  pink  

-2" 

"2" 

"2 
3 

'  13,500 
14,560 

'  18,305 
17,316 

'  11,950 

20,950 

Winkier 

Production  of  Serpentine  in  the  United  States.  —  In  the  statis- 
tical tables  annually  published  by  the  United  States  Geological 
Survey  the  production  of  serpentine,  "  verd  antique  marble,"  etc., 
is  included  with  that  of  marble,  so  that  no  exact  data  can  be 
given  in  regard  to  the  American  serpentine  production. 

Distribution  of  Serpentine.  —  Because  of  their  methods  of 
origin,  deposits  of  serpentine  are  confined  to  regions  in  which 
basic  igneous  rocks  or  highly  metamorphosed  limestones  occur. 
Deposits  of  serpentine  are  therefore  found  in  New  England,  the 
Adirondacks  and  Hudson  Highlands  of  New  York,  and  thence 
southward  in  the  Highlands  of  New  Jersey  and  the  South  Moun- 
tain, Blue  Ridge  and  Piedmont  districts  of  Pennsylvania,  Mary- 
land, Virginia,  the  Carolinas,  Alabama  and  Georgia.  Serpen- 
tine is  lacking  in  the  Ohio  and  Mississippi  valley  states,  but 
occurs  at  various  points  in  the  Rocky  Mountains  and  more 
western  areas.  The  greater  part  of  the  small  commercial  pro- 
duction comes  from  Maryland,  New  York,  New  Jersey,  Georgia,. 


SERPENTINE  AND  SOAPSTONE  87 

California  and  Washington.  For  particulars  concerning  these 
localities  reference  should  be  made  to  the  reports  in  the  following 
list. 

Reference  List  on  Serpentine.  —  Of  the  papers  in  this  list 
those  by  Mathews  and  Shedd  are  of  greatest  interest  to  the 
engineer  and  quarryman.  The  other  papers  listed  deal  largely 
or  exclusively  with  the  origin  and  geologic  relations  of  serpentine. 

Burnham,  S.  M.     History  and  uses  of  limestone  and  marble;  8vo., 

392  pp.     Boston,  1883. 
Jonas,  A.  J.     Serpentines  in  the  vicinity  of  Philadelphia.     American 

Geologist,  Vol.  36,  pp.  296-304.     Nov.,  1905. 
Lyon,  D.  A.     Serpentine  marbles  of  Washington.     Mines  and  Minerals, 

Vol.  21,  pp.  349.     1901. 
Mathews,    E.    B.     Character   and   distribution   of    Maryland   building 

stones.     Reports  Maryland  Geol.  Sur.,  Vol.  2,  pp.  125-141.     1898. 
Merrill,  F.  J.  H.     The  origin  of  the  serpentine  in  the  vicinity  of  New 

York  (City).    50th  Ann.  Rep.  N.  Y.  State  Museum,  Vol.  1,  pp.  32-44. 
Merrill,    G.    P.     On   the   serpentine   of    Montville,  N.  J.     Proceedings 

U.  S.  National  Museum,  Vol.  11,  pp.  105-111.     1889. 
Merrill,  G.  P.     A  consideration  of  some  little  known  American  orna- 
mental stones.     Stone,  Vol.  19,  pp.  225-230.     1899. 
Merrill,  G.  P.     Notes  on  the  serpentinous  rocks  of  Essex  County,  N.  Y., 

and  Easton,  Pa.     Proceedings  U.  S.  National  Museum,  Vol.   12, 

pp.  595-600.     1890. 
Newland,  D.  H.     The  serpentines  of  Manhattan   Island  and   vicinity 

and   their   accompanying   minerals.     School    of    Mines    Quarterly, 

Vol.  22,  pp.  307-317,  399-410.     1901. 
Peck,  F.  B.     Preliminary  notes  on  the  occurrence  of  serpentine  and  talc 

at  Easton,  Pa.     Annals  of  N.  Y.  Acad.  Science,  Vol.  13,  pp.  419-430. 

1901. 
Peck,  F.  B.     The  talc  deposits  of  Phillipsburg,  N.  J.,  and  Easton,  Pa. 

Ann.  Rep.  N.  J.  State  Geologist  for  1904,  pp.  161-186.     1905. 
Shedd,  S.     The  building  and  ornamental  stones  of  Washington.     Ann. 

Rep.  Washington  Geol.  Sur.  for  1902,  Vol.  2,  pp.  1-163.     1903. 
Anon.     Serpentines  of  California.     Bull.  38,  Cal.  State  Mining  Bureau, 

pp.  146-148.     1906. 

SOAPSTONE  AND  ALLIED  PRODUCTS. 

The  stones  which  are  to  be  briefly  described  in  the  present 
section  bear  a  certain  resemblance  to  serpentine  in  origin,  in 
composition  and  in  physical  characters. 

Origin  and  Composition  of  Soapstone.  —  The  soapstones  are 
rocks  which  usually  consist  largely  or  entirely  of  the  mineral 


88 


BUILDING  STONES  AND   CLAYS 


talc,  or  of  some  closely  related  mineral  species.  Talc  is  a  hydrous 
magnesian  silicate,  and  when  theoretically  pure  contains  approxi- 
mately 63  per  cent  of  silica,  32  per  cent  of  magnesia,  and  5  per 
cent  of  combined  water.  It  therefore  agrees  with  serpentine  in 
its  normal  constituents,  but  differs  from  it  in  being  both  less 
basic  and  less  hydrous.  Both  minerals  have  probably  originated, 
in  most  cases,  in  the  same  general  way,  through  the  alteration  of 
magnesian  silicate  minerals. 

Some  of  the  soapstones  which  are  utilized  commercially  differ 
from  those  above  noted  in  being  composed  largely  of  hydrous 
aluminum  silicates;  but  the  best-known  stones  are  of  the  talcose 
type. 

Distribution  and  Production.  —  Practically  all  of  the  talc  and 
soapstone  produced  in  the  United  States  is  from  deposits  located 
in  the  Green  Mountain,  Adirondack,  Highland,  Blue  Ridge  and 
Allegheny  Mountain  areas,  the  chief  producing  states  being  New 
York,  Virginia  and  Vermont.  Virginia  is  the  principal  producer 
of  soapstone,  with  Vermont  ranking  second,  for  the  output  of 
New  York  is  marketed  almost  entirely  as  ground  talc. 

The  following  statistics,  taken  from  recent  reports  of  the 
United  States  Geological  Survey,  furnish  data  as  to  the  industries 
in  question. 

TABLE  49.  —  PRODUCTION  OF  TALC  AND  SOAPSTONE 
IN  THE  UNITED  STATES,   1880-1910. 


Year. 

Short  tons. 

Value. 

Year. 

Short  tons. 

Value. 

1880-1900 

969,928 

$11,224,652 

1906 

120,644 

$1,431,556 

1901 

97,843 

908,488 

1907 

139,810 

1,531,047 

1902 

97,954 

1,140,507 

1908 

117,354 

1,401,222 

1903 

86,901 

840,060 

1909 

130,338 

1,221,959 

1904 

91,189 

940,731 

1910 

150,716 

1,592,393 

1905 

96,634 

1,082,062 

SERPENTINE  AND  SOAPSTONE 


89 


TABLE  50.  —  TALC  AND  SOAPSTONE  PRODUCTION  BY 

USES,  1907-1910. 


Condition  in  which  marketed. 

Short  tons. 

Value. 

Average 
price 
per  ton. 

Short  tons. 

Value. 

Average 
price 
per  ton. 

1907. 

1908. 

Rough  

25,538 

$34,625 

$1.36 

3,013 

$7,819 

$2.60 

Sawed  into  slabs  
Manufactured  articles  * 
Ground  f  

4,822 
23,484 
85,966 

91,668 
648,475 
756,279 

19.01 
27.61 
8.80 

3,406 
16,336 
94,599 

71,048 
442,624 

879,731 

20.86 
27.10 
9.20 

Total  J  

139,810 

1,531,047 

10.95 

117,354 

1,401,222 

11.94 

1909. 

1910. 

Rough  

27,412 

$79,499 

$2.90 

15,425 

$56,872 

$3.69 

Sawed  into  slabs 

2,893 

54,009 

18  67 

9,352 

78,042 

8  34 

Manufactured  articles  * 
Ground  f  

22,646 

77,387 

502,447 
586,004 

22.19 

7.57 

22,363 
103,576 

503,391 
954,088 

22.51 
9.21 

Total  t  

130,338 

1,221,959 

9.38 

150,716 

1,592,393 

10.57 

*  Includes  bath  and  laundry  tubs;  fire  brick  for  stoves,  heaters,  etc.;  hearthstones,  mantels, 
sinks,  griddles,  slate  pencils,  gas  tips,  burner  blanks,  crayons,  and  numerous  other  articles  for  every- 
day use. 

t  For  foundry  facings,  paper  making,  lubricators  for  dressing  skins  and  leather,  etc. 

t  Exclusive  of  the  quantity  used  for  pigment,  which  is  included  among  mineral  paints. 


TABLE  51.  — PRODUCTION  OF  TALC  AND  SOAPSTONE, 
BY   STATES,   1908-1910. 


1908. 

1909. 

1910. 

States. 

Short  tons. 

Value. 

Short  tons. 

Value. 

Short  tons. 

Value. 

Massachusetts  .... 

(*) 

(*) 

9,057 

$48,729 

7,475 

$52,204 

New    Jersey    and 

Pennsylvania.  .  . 

4,648 

$29,118 

13,900 

61,967 

13,192 

62,833 

New  York  

70,739 

697,390 

48,536 

359,957 

71,710 

728,180 

North  Carolina.  .  . 

3,564 

51,443 

5,956 

77,983 

3,887 

69,805 

Vermont  

10,755 

99,743 

23,626 

120,329 

25,975 

136,674 

Virginia  

19,616 

458,252 

26,511 

523,942 

25,908 

510,781 

Other  States  f  .  .  .  . 

8,032 

65,276 

2,752 

29,052 

2,569 

31,916 

Total  

117,354 

1,401,222 

130,338 

1,221,959 

150,716 

1,592,393 

*  Included  in  "  Other  States." 

t  Georgia,  Maryland,  Massachusetts  and  Rhode  Island,  in  1908 ;  California,  Georgia,  Mary, 
land  and  Rhode  Island,  in  1909  and  1910. 


90 


BUILDING  STONES  AND  CLAYS 


TABLE    52.— TALC    IMPORTED    INTO    THE    UNITED    STATES, 

1902-1910. 


Year. 

Short  tons. 

Value. 

Average 
price  per 
ton. 

Year. 

Short  tons. 

Value. 

Average 
price  per 
ton. 

1902 

2,859 

$35,366 

$12.36 

1907 

10,060 

$126,391 

$12.56 

1903 

1,791 

19,677 

10.99 

1908 

7,429 

97,096 

13.07 

1904 

3,268 

36,370 

11.13 

1909 

4,417 

56,287 

12.74 

1905 

4,000 

48,225 

12.05 

1910 

8,378 

106,460 

12.71 

1906 

5,643 

67,818 

12.02 

References  on  Talc  and  Soapstone.  —  The  following  list  con- 
tains the  titles  of  a  number  of  papers  and  reports  which  can  be 
consulted  for  further  data  on  talc  and  soapstone,  to  supplement 
the  necessarily  brief  discussion  in  the  present  volume. 

Keith,  A.     Talc  deposits  of  North  Carolina.     Bull.  213,  U.  S.  Geol.  Sur., 

pp.  433-438.     1903. 
Nevius,  J.  N.     Fibrous  talc  in  St.  Lawrence  County,  New  York.     Eng.  & 

Mining  Jour.,  Vol.  67,  pp.  234,  235.     1899. 
Nevius,  J.  N.     The  talc  industry  of  St.  Lawrence  County,  New  York. 

51st  Ann.  Rep.  N.  Y.  State  Museum,  Vol.  1,  pp.  122-127.     1899. 
Peck,  E.  B.     The  talc  deposits  of  Phillipsburg,  N.  J.,  and  Easton,  Pa. 

Ann.  Rep.  N.  J.  State  Geologist  for  1904,  pp.  161-186.     1905. 
Pratt,  J.  H.     Talc  and  pyrophyllite  deposits  in  North  Carolina.     Eco- 
nomic Paper,  No.  3,  N.  C.  Geol.  Sur.,  29  pp.     1900. 
Sahlin,  A.     The  talc  industry  of  the  Gouverneur  district,  New  York. 

Trans.  Amer.  Inst.  Min.  Eng'rs,  Vol.  21,  pp.  583-588.     1893. 
Smyth,  C.  H.     Report  on  the  talc  industry  of  St.  Lawrence  County, 

N.  Y.     15th  Ann.  Rep.  N.  Y.  State  Geologist,  Vol.  1,  pp.  661-671. 

1897. 
Perkins,  G.  H.     Soapstone  in  Vermont.     Rep.  Vt.  State  Geologist  for 

1899-1900,  pp.  77-79.     1900. 
Watson,  T.  L.     Talc  and  soapstone  in  Virginia.     Mineral  Resources  of 

Virginia,  Richmond,  1907,  pp.  289-296. 


CHAPTER  VI. 
SEDIMENTARY  ROCKS  IN  GENERAL. 

THE  products  which  have  been  discussed  in  the  preceding  chap- 
ters of  this  volume  are  all,  either  directly  or  indirectly,  of  igneous 
origin.  The  stones  which  remain  to  be  considered  —  the  slates, 
sandstones,  limestones  and  marbles  —  are,  on^  the  other  hand,  of 
sedimentary  origin.  In  order  to  keep  a  proper  sense  of  propor- 
tion it  seems  desirable,  before  taking  up  the  classes  of  sedimentary 
'rocks  separately,  to  devote  a  short  chapter  to  the  consideration 
of  the  entire  group.  It  will  thus  be  possible  to  discuss  both  the 
resemblances  of  the  group,  and  the  differences  of  the  sub-classes, 
from  a  broader  basis  than  is  available  when  only  one  of  the  sub- 
classes is  under  consideration. 

The  Basis  for  Classification.  —  Geologists  and  petrographers 
who  have  devoted  most  of  their  lives  to  the  study  of  the  igneous 
rocks,  have  fallen  into  one  curious  error  of  fact  with  regard  to 
the  sedimentary  rocks.  When  an  error  once  reaches  the  dignity 
of  print,  it  is  capable  of  a  surprising  tenacity  of  life ;  for  the  human 
parrots  who  are  responsible  for  much  of  our  literature  rarely 
check  up  their  compilations  by  either  research  or  thought.  The 
result,  in  this  particular  case,  is  the  common  assumption  that  the 
classification  of  the  sedimentary  rocks  is  less  natural  and  less 
exact  than  that  of  the  igneous  rocks. 

In  every  publication  on  the  subject  that  has  come  to  the  notice 
of  the  writer,  the  assumption  is  made,  either  explicitly  or  im- 
plicitly, that  the  various  classes  of  sedimentary  rocks  show  such 
an  infinite  series  of  gradations,  so  far  as  chemical  composition  is 
concerned,  as  to  render  a  sharply  defined  classification  impossible. 
In  this  respect  the  sedimentary  rocks  are  invariably  contrasted 
unfavorably  with  the  igneous  rocks,  where  such  definite  classi- 
fication is  held  to  be  possible.  As  a  matter  of  fact,  the  real 
conditions  are  exactly  the  reverse  of  those  set  forth  by  our  text- 
book writers,  for  it  is  the  sedimentary  rocks  which  show  the 
sharpest  chemical  differences,  and  the  greatest  gaps  between 

91 


92 


BUILDING  STONES  AND  CLAYS 


classes.  It  is  therefore  feasible  to  classify  sedimentary  rocks 
on  a  purely  chemical  basis;  and  in  the  classification  thus  estab- 
lished relatively  few  intermediate  links  will  be  found. 

Classes  of  Sedimentary  Rocks.  —  A  convenient  working  classi- 
fication of  the  sedimentary  rocks,  satisfactory  enough  for  our 
present  purposes,  is  that  following.  It  will  be  seen  that  these 
rocks  can  be  divided  into  three  fairly  distinct  groups,  the  basis 
for  the  division,  as  given  below,  being  partly  chemical  and 
partly  physical.  In  later  sections  the  sharpness  of  the  chemical 
distinctions  between  the  groups  will  be  more  strikingly  illustrated. 

(1)  Siliceous  sediments;  composed  of  grains  or  pebbles,  usually 
of  quartz  —  sandstones,  conglomerates. 

(2)  Argillaceous  sediments;  composed  of  clayey  materials  — 
shales,  slates. 

(3)  Calcareous   sediments;    composed   largely    or    entirely    of 
carbonate   of   lime,    with   or   without    carbonate    of    magnesia 

—  limestones,  dolomites,  marbles. 

Degree  of  Consolidation.  —  It  may  here  be  noted  that  the 
geologist,  in  speaking  of  rocks,  includes  not  only  the  hard  materials 
commonly  known  by  that  name  but  also  the  soft,  unconsolidated 
phases  of  these  same  materials,  i.e.,  sands,  gravels,  clays,  marls, 
etc.  This  introduces  a  cross  classification,  based  on  the  degree 
of  consolidation  of  the  material,  as  indicated  in  the  little  table 
following : 


Degree  of  consolidation. 

Kind  of  rock. 

Entirely  uncon- 
solidated. 

Normally  consolidated. 

Metamorphosed, 
extremely  consoli- 
dated. 

Siliceous  rocks.  .  .  . 
Argillaceous  rocks. 

Sand,  gravel 
Clays  

Sandstones,  conglomerates. 
Shales  

Quartzites 
Slates,  schists 

Calcareous  rocks 

Marls 

Limestones  .  . 

Marbles 

Modes  of  Origin  of  Sediments.  —  With  the  exception  of  a  few 
relatively  unimportant  instances  where  ice  or  wind  have  played 
some  part  in  the  deposition  of  rocks,  all  of  the  sedimentary  rocks 
have  been  deposited  in  bodies  of  water.  In  most  cases  water 
has  been  both  the  transporting  and  the  depositing  agent,  but 
chemical  and  organic  agencies  have  in  many  instances  affected 
the  result. 


SEDIMENTARY  ROCKS  IN  GENERAL  93 

In  the  case  of  a  sandstone  deposit,  for  example,  the  sand  grains 
of  which  it  is  composed  were  transported  by  flowing  water  to 
some  point  at  which  the  current  was  checked.  The  deposition 
of  the  sand  took  place,  therefore,  from  purely  mechanical  causes. 
Clay  and  shale  beds  are,  in  most  cases,  due  to  causes  just  as 
purely  mechanical  as  are  the  sand  beds. 

In  the  case  of  limestones,  however,  two  entirely  different  sets 
of  agencies  have  often  taken  part  in  the  process.  This  arises 
from  the  fact  that  lime  carbonate,  as  transported  by  running 
water,  is  carried  in  solution  and  not  in  suspension.  The  simple 
checking  of  the  current  will  therefore  be  insufficient,  under 
ordinary  conditions,  to  produce  the  deposition  of  limestone. 
Such  deposition  can  be  caused,  however,  either  by  chemical 
agencies  acting  on  the  lime-charged  water,  or  by  the  action  of 
organisms.  In  one  case  the  lime  carbonate  may  be  deposited 
through  evaporation;  in  the  other  case  it  may  be  extracted  from 
the  water  by  organisms,  and  will  then  form  a  bed  of  limestone 
when  these  organisms  finally  sink  to  the  bottom. 

Characteristic  Sedimentary  Structures.  —  The  most  charac- 
teristic feature  about  sedimentary  rocks,  as  distinguished  from 
igneous  rocks,  is  the  fact  that  the  sediments  are  almost  invariably 
divided  into  beds  or  layers.  This  characteristic  feature  arises 
from  the  fact  that  sedimentation  is  never  absolutely  continuous 
and  uniform.  Variations  in  the  water  level,  in  the  direction  of 
currents,  or  in  composition  of  the  particles  of  material  carried  by 
the  water  in  suspension  —  all  of  these  have  an  influence  in  this 
matter.  Even  slight  changes  in  the  composition  of  the  deposit 
are  apt  to  be  reflected  by  differences  of  color,  texture,  etc., 
which  suffice  to  mark  out  the  bedding  planes  of  the  resulting 
rock. 

Metamorphism  and  Its  Effects.  —  The  metamorphism  of  sedi- 
mentary rocks  changes  their  character  and  appearance  in  many 
ways,  but  these  changes  are  usually  almost  entirely  physical, 
and  are  accompanied  by  less  chemical  alteration  than  might  be 
supposed.  This  point  is  brought  out  conclusively  in  later  chap- 
ters where  the  alteration  of  limestone  to  marble,  of  clayey  sedi- 
ments to  slates,  and  of  sandstones  to  quartzites  are  discussed  in 
some  detail. 

Normal  Order  of  Discussion.  —  In  the  succeeding  chapters  of 
this  volume  the  sedimentary  building  stones  will  be  taken  up 


94  BUILDING  STONES  AND  CLAYS 

separately  and  described  in  detail.  The  order  in  which  these 
sub-classes  will  be  discussed  is  as  follows: 

Chapter  VII. -Slates. 

Chapter  VIII.  —  Sandstones. 

Chapter  IX.  —  Limestones. 

Chapter  X.  —  Marbles. 

This  order  of  discussion  is  the  normal  one  to  adopt,  if  the  origin 
and  general  relations  of  these  sub-classes  be  kept  in  mind.  The 
slates  are,  so  far  as  genesis  and  chemical  composition  are  con- 
cerned, the  most  closely  related  to  the  igneous  rocks  and  should 
therefore  be  considered  first.  The  sandstones  and  limestones, 
on  the  other  hand,  represent  products  whose  composition  has, 
by  mechanical  or  chemical  selection,  become  sharply  differen- 
tiated from  that  of  the  average  igneous  rock. 


CHAPTER  VII. 
SLATES. 

THE  slates  are  rocks,  normally  clayey  in  composition,  in  which 
pressure  has  produced  a  very  perfect  cleavage,  so  that  a  block 
of  slate  can  be  readily  split  into  thin,  smooth,  tough  plates. 

ORIGIN  AND   COMPOSITION. 

Origin  of  Slates.  —  Almost  all  commercial  slates  have  origi- 
nated through  the  action  of  pressure  on  fine-grained,  clayey  sedi- 
mentary rocks;  but  a  few  well-known  roofing  slates  have  been 
produced,  by  the  same  agency,  from  deposits  of  volcanic  ash  or 
from  rocks  of  even  more  direct  igneous  origin.  Though  these 
igneous  slates  are  of  great  interest  scientifically,  the  normal  or 
clayey  slates  are  much  more  important.  The  following  discus- 
sion therefore  will  consider  primarily  the  origin  of  the  clay 
slates,  after  which  the  origin  of  the  igneous  slates  will  be  briefly 
noted.  Wherever,  in  this  chapter,  the  term  slate  is  used  without 
any  qualification,  it  should  be  understood  to  refer  to  the  slates 
derived  from  sedimentary  clay  rocks. 

The  first  stage  in  the  origin  of  a  slate  is  the  deposition,  in 
relatively  quiet  water,  of  fine-grained  clayey  material.  No  con- 
ceivable pressure  can  succeed  in  making  a  serviceable  slate  out 
of  a  coarse-grained  sediment,  out  of  a  bed  of  sand,  or  out  of  a 
noticeably  calcareous  deposit.  So  that  unless  the  original  sedi- 
mentary deposit  is  of  the  proper  physical  constitution,  no  slate 
deposit  can  be  formed  from  it.  Now,  it  happens  that  the  proper 
fineness  and  plasticity  can  be  readily  secured  in  deposits  of  clay, 
but  that  they  are  very  difficult  and  almost  impossible  to  secure 
if  the  deposit  consists  of  siliceous  or  limy  matter.  For  this 
reason,  slates  show  a  surprising  uniformity  in  chemical  compo- 
sition —  a  fact  which  usually  is  either  overlooked  or  passed  by 
as  a  matter  of  course. 

If  the  clay  bed  so  formed  be  allowed  to  consolidate  under 
entirely  normal  conditions,  a  bed  of  shale  will  be  the  ultimate 

95 


96  BUILDING  STONES  AND   CLAYS 

result.  This  will  carry  almost  as  much  combined  water  as  did 
the  original  clay,  will  have  practically  the  same  mineral  con- 
stitution, and  will  show  no  regular  cleavage  system,  breaking  on 
the  contrary  into  irregular  blocks.  In  a  later  section  of  this 
volume,  when  dealing  with  the  subject  of  clays,  further  data 
on  shale  deposits  will  be  presented.  At  present,  however,  their 
interest  arises  from  the  fact  that  many  of  them  might  have 
become  slates  under  more  favorable  conditions. 

In  regions  where  earth  movements  have  exerted  heavy  and 
long-continued  pressure  on  the  rocks,  certain  physical  .  and 
chemical  changes  have  often  been  the  results.  The  limestones 
may  be  recrystallized  into  marbles;  the  sandstones  may  become 
quartzites;  and  some  of  the  fine-grained  clayey  rocks  may  become 
slates.  In  all  of  these  metamorphic  effects,  the  physical  changes 
are  the  more  important  and  noticeable;  but  in  some  instances 
chemical  changes  have  also  accompanied  them.  In  the  case  of 
the  formation  of  slates  the  physical  changes  are  the  only  ones 
which  really  require  consideration  at  any  length. 

The  chief  difference  between  a  roofing  slate  and  an  ordinary 
clay  or  shale  is  that  the  slate  will  cleave  readily  into  thin  plates, 
which  plates  may  or  may  not  be  parallel  to  the  original  bedding 
planes,  while  the  clays  and  shales  break  into  more  irregular 
masses,  the  easiest  breaking  planes  being  either  parallel  to  the 
bedding  or  parallel  to  joint  systems.  It  has  been  proven  experi- 
mentally that  the  distinctive  slaty  cleavage  can  be  produced  in 
any  fine-grained  homogeneous  mass  by  long-continued  heavy 
pressure,  so  that  we  may  fairly  assume  that  the  cleavage  of 
roofing  slates  is  produced  in  this  way.  The  character  of  this 
cleavage,  and  its  relation  to  the  original  bedding  planes,  will  be 
discussed  on  a  later  page. 

Average  Chemical  Composition  of  Slates.  —  The  following 
average  analysis  of  roofing  slate  has  been  prepared  by  the  writer 
from  a  long  series  of  analyses  of  commercial  slates  quarried  in 
various  American  districts. 


SLATES 


97 


TABLE  53. —  AVERAGE  COMPOSITION  OF  FORTY-SEVEN 
AMERICAN  ROOFING  SLATES. 


Constituent. 

Number  of  de- 
terminations 
averaged. 

Alininiuni. 

Average. 

Maximum. 

Silica  

44 

54.05 

61.43 

69.08 

Alumina  *  

43 

8.62 

17.33 

24.71 

Ferric  oxide 

20 

0  52 

2  24 

7  10 

Ferrous  oxide  

20 

0.97 

3.85 

7.48 

Lime  . 

45 

0  00 

1  58 

5.23 

Magnesia.  . 

45 

0  12 

2.47 

6.43 

Potash  

•    36 

0.72 

3.46 

5.54 

Soda  

36 

0.09 

1.11 

3.15 

Iron  sulphide  

18 

0.38 

Carbon  dioxide  

16 

1.47 

Combined  water 

15 

3  51 

Moisture  .... 

16 

0  62 

Total  silica  and  alumina.  . 

47 

78  76 

Total  iron  oxides  

44 

7  40 

Total  lime  and  magnesia.  . 
Total  alkalies  

45 
40 

4.05 
4.47 

Total  water  and  CO2 

16 

5  60 

*  Titanic  oxide  is  included  with  the  alumina  in  this  table.  In  nineteen  of  the  analyses  considered, 
the  titanic  oxide  had  been  separately  determined.  The  average  of  these  nineteen  determinations 
gave  0.73  per  cent  titanic  oxide. 


Average  Composition  of  Shales.  —  In  Bulletin  168,  United 
States  Geological  Survey,  on  pages  16  and  17,  Pr.  Clarke  has 
quoted  a  series  of  composite  analyses  of  American  sedimentary 
rocks.  The  material  was  selected  and  the  samples  were  pre- 
pared by  Mr.  G.  K.  Gilbert,  assisted  by  Mr.  G.  W.  Stose,  and 
the  analyses  were  made  by  Dr.  H.  N.  Stokes  in  the  chemical 
laboratory  of  the  Survey. 

These  composite  analyses,  so  far  as  they  relate  to  shales,  are 
reprinted  here  as  Table  54.  The  determinations  of  a  number  of 
minor  constituents  are  omitted.  In  this  series  each  individual 
shale  was  taken  in  amount  roughly  proportional  to  the  mass  of 
the  formation  which  it  represented.  The  samples  were  then 
mixed  into  one  uniform  sample  from  which,  by  a  single  analysis, 
an  average  composition  was  determined. 

In  column  1  is  given  the  result  of  an  analysis  of  twenty-seven 
Mesozoic  and  Cenozoic  shales;  and  in  column  2  that  of  fifty- 
one  Paleozoic  shales.  Column  3  gives  the  average  of  these  two 
determinations,  giving  them,  respectively,  weights  as  3  to  5. 


98 


BUILDING  STONES  AND   CLAYS 


The  values  in  this  column  are,  therefore,  an  approach  to  the 
"  average  shale  "  composition. 

TABLE  54.  —  COMPOSITE  ANALYSES  OF  AMERICAN  SHALES. 


1 

2 

3 

Silica  (SiO2) 

55  43 

60  15 

58  38 

Alumina  (A^Os) 

13.84 

16  45 

15  47 

Titanic  oxide  (TiO2)  ... 

0  46 

0  76 

0  65 

Ferrous  oxide  (FeO)  

1.74 

2  90 

2  46 

Ferric  oxide  (Fe2Oa)  

4.00 

4.04 

4.03 

Lime  (CaO) 

5  96 

1  41 

3  12 

Magnesia  (MgO) 

2  67 

2  32 

2  45 

Potash  (K2O) 

2  67 

3  60 

3  25 

Soda  (Na2O) 

1.80 

1  01 

1.31 

Carbon  dioxide  

4.62 

1.46 

2.64 

Water  of  combination  

3.45 

3.82 

3.68 

Moisture,  below  110°  C  

2.11 

0.89 

1.34 

It  may  be  noted  in  passing  that  some  of  the  differences  in 
composition  between  the  Paleozoic  and  the  later  shales  were, 
either  in  degree  or  in  kind,  contrary  to  what  might  have  been 
expected,  from  a  purely  theoretical  standpoint. 

Comparison  of  Slate  and  Shale  Average  Analyses.  —  It  is  of 
interest  to  compare  the  two  long  series  of  slate  and  shale  analyses 
presented  in  the  two  preceding  sections,  with  a  view  to  getting 
some  idea  of  the  relative  chemical  composition  of  the  two  classes 
of  rock.  As  almost  all  of  the  slate  analyses  were  of  Paleozoic 
slates,  it  is  obvious  that  the  average  slate  should  be  most  directly 
comparable  with  the  composite  analysis  of  fifty-one  Paleozoic 
shales,  given  in  column  2  of  Table  54.  The  necessity  for  thus 
restricting  the  comparison  is  accentuated  by  the  fact,  above 
intimated,  that  the  Paleozoic  and  later  shales  are  not  themselves 
directly  comparable. 

The  average  slate  contains  61.43  per  cent  of  silica,  as  against 
60.15  in  the  average  Paleozoic  shale.  Alumina  and  titanic  oxide 
together  amount  to  17.33  in  the  slate,  and  to  17.21  in  the  shale, 
the  titanic  oxide  alone  being  practically  the  same  in  both.  The 
slate  is  high  in  ferrous  oxide,  and  the  shale  in  ferric  oxide;  but 
the  total  iron  oxides  in  the  slate  amount  to  7.40  per  cent,  as 
against  6.94  in  the  shale.  Lime  and  magnesia  together  are  4.05 
in  the  slate,  and  3.73  in  the  shale;  and  total  alkalies  are  still 
closer,  being  4.47  in  the  slate,  and  4.61  in  the  shale.  Carbon 


SLATES  99 

dioxide,  combined  water  and  moisture  are  also  almost  exactly 
the  same  in  the  two  rocks.  Carbonates,  as  rock-forming  min- 
erals, introduce  an  element  of  weakness:  and  their  presence  in 
undue  quantity  in  any  given  slate  must  therefore  be  regarded 
with  suspicion. 

The  conclusion  to  be  drawn  from  this  comparison  is  that  the 
average  roofing  slate  is  almost  absolutely  identical  in  chemical 
composition  with  the  average  shale;  and  that  the  two  differ  only 
in  their  physical  characters.  During  the  change  from  shale  to 
slate  —  or  rather  from  clay  to  slate  or  shale  —  the  slate  assumed 
perfect  cleavage,  but  its  composition  was  practically  unaltered. 

Origin  and  Composition  of  Igneous  Slates.  —  There  are  two 
classes  of  slates  now  quarried  to  both  of  which  the  term  igneous 
slates  may  be  fairly  applied,  though  they  are  really  very  different 
in  origin.  The  first  class  would  include  slates  formed  from 
deposits  of  volcanic  ash;  the  second  class  would  include  slates 
formed  from  actual  igneous  rocks. 

(1)  The  ash  slates  have  been  known  and  quarried  for  a  long 
time,  the  best- known  examples  of  this  type  being  the  slates  from 
the  Lake  district  of  England.  Dale*  has  summarized  recently 
published  descriptions  of  these  slates  as  follows: 

"  Most  remarkable  are  the  green  slates  from  the  English  Lake 
district  (Buttermere,  Tilberthwaite,  etc.),  which  consist  of  vol- 
canic ash  and  which  have  long  been  known  in  England  as  ex- 
cellent roofing  material.  These  have  recently  been  chemically 
and  microscopically  analyzed  and  described.  These  slates  are 
found  to  consist  chiefly  of  chlorite,  calcite,  quartz  (mostly  second- 
ary), and  muscovite,  but  contain  also  andesitic  lapilli,  feldspar, 
garnets,  sphene  and  anatase.  Slate  needles  and  tourmaline  are 
conspicuously  absent.  The  chemical  analyses  show  the  follow- 
ing important  constituents: 

SiO2 60.16-54.02 

A12O3 11 .94-17 .85 

CaO 3.67-  6.46 

FeO 5.97-  7.06 

CO2 2.45-  5.41 

CO2  if  calculated  to  CaCO3  would  give  from  5.56  to  12.29  per 
cent  of  CaC03.  Specific  gravity  ranges  from  2.775  to  2.788. 

*  Bull.  275,  U.  S.  Geol.  Sur.,  p.  18.     1906. 


100 


BUILDING  STONES  AND  CLAYS 


The  percentage  of  SiO2  is  low,  and  that  of  FeO  is  near  that  of 
the  "  unfading  green  "  slate  of  Vermont." 

(2)  The  sheared  igneous  slates  are  a  still  more  remarkable  class. 
These  were  first  identified  and  described*  by  the  present  writer 
in  1903,  who  found  them  worked  at  the  quarry  of  the  Eureka 
Slate  Company,  north  of  Placerville,  California.  The  igneous 
slates  here  appear  as  narrow  bands  extending  vertically  from 
top  to  bottom  of  the  quarry  wall,  the  main  mass  of  the  wall  being 
a  glossy  black  slate  of  normal  sedimentary  origin. 

A  typical  specimen  of  the  green  slate,  from  near  the  middle 
of  the  band,  was  selected  for  partial  analysis  in  the  laboratory 
of  the  United  States  Geological  Survey,  and  the  results  of  this 
analysis  are  presented  below,  as  No.  1.  The  second  analysis 
given  below  was  quoted  to  the  writer  by  Mr.  C.  H.  Dunton, 
manager  of  the  Eureka  Slate  Company,  but  the  name  of  the 
analyst  was  unknown  to  him.  The  two  analyses  agree  suf- 
ficiently closely,  and  are  probably  fairly  representative  of  the 
chemical  composition  of  the  green  slates. 

ANALYSES   OF   THE    " GREEN   SLATES"  FROM    SLATINGTON, 

CALIFORNIA. 


1 

2 

Silica  (SiO2)  

45  15 

47  30 

Alumina  (A12O3)  and  titanic  oxide  (TiO2)  
Iron  oxides  (FeO,  Fe2O3) 

16.33 

8  42 

15.53 

8  00 

Lime  (CaO) 

6  42 

7  83 

Magnesia  (MgO) 

8  72 

7  86 

Alkalies  (Na2O,  K2O)   

n.d. 

3  17 

Carbon  dioxide  (CO2)  ) 

Wafpr                                                          (     

11.28 

9.92 

1.  By  W.  T.  Schaller,  U.  S.  Geological  Survey  Laboratory. 

2.  Analyst  unknown.     Analysis  quoted  by  Eureka  Slate  Co. 

It  will  be  seen  that  these  analyses  differ  widely  from  those  of 
any  normal  clay  slate,  and  even  if  no  structural  evidence  were 
at  hand,  the  chemical  composition  of  the  green  slate  would  be 
sufficient  to  suggest  that  their  origin  was  probably  from  igneous, 
not  sedimentary,  rocks. 

*  Eckel,  E.  C.     On  a  California  roofing  slate  of  igneous  origin.     Journal 
of  Geology,  Vol.  XII,  pp.  15-24. 


SLATES 

The  evidence  gathered  as  a  result  of  further  study  of  this 
occurrence  may  be  summarized  as  follows: 

1.  The  structural  relations  of  the  green  and  the  black  slates 
seem  to  prove  that  the  green  slates  are  derived,  by  dynamic 
metamorphism,  from  an  igneous  rock;  further,  that  this  rock 
was  an  intrusive  massive  rock,  not  an  interbedded  tuff;  and  that 
it  was  intruded  into  the  Mariposa  slates  at  some  period  subse- 
quent to  their  deposition,  but  before  their  assumption  of  slaty 
cleavage. 

2.  Microscopic  evidence,  though  inconclusive,  owing  to  the 
lack  of  a  sufficient  supply  of  material,  proves  that  the  green 
slates  are   composed  of  thoroughly  crystalline  material.     The 
rock    forming  one   of  the    near-by    dikes    is    shown    to    be    a 
gabbro. 

3.  Chemical  analyses  of  the  green  slates  show  that  they  are 
widely   different   in   composition   from   the   black   slates,    and, 
indeed,  from  any  normal  clay  slate.     Comparison  of  the  same 
analyses  with  those  of  igneous  rocks  of  the  region  show  striking 
similarities  in  composition  between  the  green  slates  and  certain 
massive,  basic,  igneous  rocks  —  gabbros  and  allied  rocks. 

There  are,  of  course,  no  reasons  why  an  igneous  rock  should 
not  be  susceptible  of  change,  under  proper  conditions,  into  a 
roofing  slate;  and  the  possibility  of  such  a  change  occurring 
would  probably  have  been  conceded  by  most  geologists,  had  the 
question  been  brought  to  their  attention,  before  the  foregoing 
description  of  an  actual  occurrence  had  been  published.  Not- 
withstanding these  facts,  the  California  occurrence  seems  to  be 
unique.  The  extensive  literature  of  roofing  slate  has  been  ex- 
amined by  the  writer,  so  far  as  this  literature  is  available,  and 
no  similar  occurrences  of  the  derivation  of  roofing  slates  from 
massive  igneous  rocks  have  been  noted.  More  than  this,  the 
possibility  of  such  an  occurrence  would  seem  to  have  been  over- 
looked by  most  writers,  who  either  expressly  or  by  implication 
use  the  term  "  roofing  slate  "  to  include  only  argillaceous  sedi- 
mentary rocks.  This  oversight  is  the  more  inexcusable,  because 
a  large  industry  has  been  based  for  a  century  or  more,  in  one 
English  district,  on  roofing  slates  derived  from  tuffs. 

List  of  References  on  Origin  and  Composition  of  Slate.  —  The 
following  list  covers  a  few  of  the  many  papers  dealing  with  the 
origin  and  composition  of  slates. 


102  BTllLDING  STONES  AND  CLAYS 

Becker,  G.  F.     Finite  homogeneous  strain,  flow,  and  rupture  of  rocks. 

Bull.  Geol.  Soc.  America,  vol.  4,  pp.  13-90.     1893. 
Becker,  G.  F.     Schistosity  and  slaty  cleavage.     Jour,  of  Geol.,  vol.  4, 

pp.  429-448.     1896. 
Becker,  G.  F.     Experiments  on  schistosity  and  slaty  cleavage.     Bulk 

241,  U.  S.  Geol.  Sur.     1904. 
Cole,    G.     Phyllade,  phyllite,   and   ottrelite.     Geol.    Mag.,   new  series, 

decade  IV,  vol.  3,  pp.  79-81.     1896. 
Dale,  T.  N.     Slate  deposits  and  slate  industry  of  the  United  States. 

Bull.  275,  U.  S.  Geol.  Sur.,  154  pp.    1906. 
Eckel,  E.   C.     On  the  chemical  composition  of  American  shales  and 

roofing  slates.    Jour,  of  Geol.,  vol.  12,  pp.  25-29.     1904. 
Eckel,  E.  C.     On  a  California  roofing  slate  of  igneous  origin.     Jour,  of 

Geol.,  vol.  12,  pp.  15-24.     1904. 
Barker,  A.     On  slaty  cleavage  and  allied  rock  structures.     Rep.  British 

Assoc.  Adv.  Science  for  1885.     1886. 
Hunt,  A.  R.     Notes  on  petrological  nomenclature;  schist,  slate,  phyllade, 

and  phyllite.     Geol.  Mag.,  new  series,  decade  IV,  vol.  3,  pp.  31-35. 

1896. 
Hutchings,  W.  M.     Notes  on  the  probable  origin  of  some  slates.     Geol. 

Mag.,  new  series,  decade  III,  vol.  7,  pp.  264-273,  316-322.     1890. 
Hutchings,  W.  M.     Notes  on  the  ash  slates  and  other  rocks  of  the  Lake 

district.     Geol.  Mag.,  new  series,  decade  III,  vol.  9,  pp.  154-161, 

218-228.     1892. 
Hutchings,  W.  M.     Notes  on  the  composition  of  clays,  slates,  etc.;  and 

on  some  points  in  their  contact  metamorphism.     Geol.  ,Mag.,  new 

series,  decade  IV,  vol.  1,  pp.  36-45,  64-75.     1894. 
Hutchings,  W.  M.     An  interesting  contact  rock,  with  notes  on  contact 

metamorphism.     Geol.  Mag.,  new  series,  decade  IV,  vol.  2,  pp.  122- 

131,  163-169.     1895. 
Hutchings,  W.  M.     Note  on  a  contact  rock  from  Shap.  Geol.  Mag.,  new 

series,  decade  IV,  vol.  2,  pp.  314-317.     1895. 
Hutchings,  W.  M.     Clays,  shales,  and  slates.     Geol.  Mag.,  new  series, 

decade  IV,  vol.  3,  pp.  309-317,  343-350.     1896. 
Hutchings,  W.  M.     The  contact  rocks  of  the  great  Whin  Sill.     Geol. 

Mag.,  new  series,  decade  IV,  vol.  5,  pp.  69-82,  123-131.     1898. 
Reade,  T.  M.,  and  Holland,  P.     The  green  slates  of  the  Lake  district,  with 

a  theory  of  slaty  cleavage  and  slaty  structure.     Proc.  Liverpool  Geol. 

Soc.  for  1900-1901,  pp.  101-127.     1901. 
Spring,  W.     Sur  les  conditions  dans  lesquelles  certains  corps  prennent 

la  texture  schisteuse.     Archives  des  sciences  phys.  et  nat.  de  Geneve, 

vol.  13,  pp.  329-341.     1893. 

Analyses  of  Slates  from  Various  Localities.  —  The  following 
series  of  tables  (Tables  55  to  61  inclusive)  contain  the  results 
of  a  large  number  of  analyses  of  roofing  slates  from  various 
localities  in  the  United  States  and  elsewhere. 


SLATES 


103 


TABLE 55.  —  ANALYSES  OF  SLATES:    MAINE  AND 
MASSACHUSETTS. 


i 

2 

3 

Silica  

56.42 

54.24 

60.80 

Alumina                                         

24.14 

24.71 

22.00 

Ferric  oxide                     

4.46 

8.39 

10.50 

Lime                         

0.52 

5.23 

0.50 

JVIagnesia 

2  28 

2.59 

0  70 

Potash  

5.53 

0.72 

1.50 

Soda 

3.15 

1.43 

0.80 

1.  Monson  Slate  Company,  Monson,  Me.;  L.  M.  Norton,  analyst;  20th 

Ann.  Rep.  U.  S.  Geol.  Survey,  pt.  6,  p.  394. 

2.  Monson,  Me.;  no  analyst  given;  quoted  in  same  publication. 

3.  Lancaster,  Mass.;  no  analyst;  18th  Ann.  Rep.  U.  S.  Geol.  Sur.,  pt.  5r 

p.  999.     Probably  mica  schist. 

TABLE  56.  —  ANALYSES  OF  SLATES  :   NEW  YORK, 
VERMONT. 


l 

2 

3 

4 

5 

6 

7 

8 

9 

Silica 

67.61 
13.20 
0.56 
5.36 
1.20 
0.11 
3.20 
4.45 
0.67 
0.03 

'3A2 

67.55 
12.59 
0.58 
5.61 
1.24 
0.26 
3.27 
4.13 
0.61 
0.04 
0.11 
3.43 

56.49 
11.59 
0.48 
3.48 
1.42 
5.11 
6.43 
3.77 
0.52 
0.03 
7.42 
3.19 

63.88 
9.77 
0.47 
3.86 
1.44 
3.53 
5.37 
3.45 
0.20 
tr. 
5.08 
2.75 

67.89 
11.03 
0.49 
1.47 
3.81 
1.43 
4.57 
2.82 
0.77 
0.04 
1.89 
3.57 

59.27 
18.81 
0.99 
1.12 
6.58 
0.42 
2.21 
3.75 
1.88 
0.15 
0.21 
4.30 

60.24 
18.46 
0.92 
2.56 
5.  IS 
0.33 
2.32 
4.  OS 
1.57 

o.ie 

0.05 
3.9€ 

60.96 
16.15 
0.86 
5.16 
2.54 
0.71 
3.06 
5.01 
1.50 

'o.'es 

3.25 

61.63 
16.33 
0.68 
4.10 
2.71 
0.50 
2.92 
5.54 
1.26 
0.04 
0.41 
3.55 

Alumina                    .... 

Titanic  oxide  

Ferric  oxide  

Ferrous  oxide  

Lime  

Magnesia  

Potash 

Soda   .                      ... 

Iron  sulphide    

Carbon  dioxide  

Water  

10 

11 

12 

13 

14 

15 

16 

17 

Silica 

65.29 

59.70 
16.98 
0.79 
0.52 
4.88 
1.27 
3.23 
3.77 
1.35 
1.18 
1.40 
4.12 

59.84 
15.02 
0.74 
1.23 
4.73 
2.20 
3.41 
4.48 
1.12 
0.05 
2.98 
3.85 

62.37 
15.43 
0.74 
1.34 
5.34 
0.77 
3.14 
4.20 
1.14 
0.06 
0.87 
4.05 

67.76 
14.12 
0.71 
0.81 
4.71 
0.63 
2.38 
3.52 
1.39 
0.22 
0.40 
3.21 

59.48 
18.22 
1.02 
1.24 
6.81 
0.56 
2.50 
3.81 
1.55 
0.13 
0.39 
4.22 

60.72 
22.59 
0.57 

'6^03' 
0.41 
2.05 
3.69 
0.86 
n.d. 
n.d. 
3.01 

58.15 
18.93 
0.93 
2.91 
5.64 
0.60 
2.70 
3.92 
1.17 
n.d. 
n.d. 
4.56 

Alumina 

Titanic  oxide      .      ... 

Ferric  oxide  

Ferrous  oxide  

Lime 

Magnesia 

Potash  .  .  . 

Soda  

Iron  sulphide  

Carbon  dioxide 

Water  .    . 

104 


BUILDING  STONES  AND  CLAYS 


Analyses  1-15  inclusive  of  the  above  table  are  by  W.  F.  Hille- 
brand,  and  are  quoted  from  the  nineteenth  Annual  Report  United 
States  Geological  Survey,  part  3,  page  232,  et  seq.  Analyses 
16  and  17  are  by  L.  G.  Eakins,  and  are  quoted  from  Bulletin 
168,  United  States  Geological  Survey,  page  280.  The  localities 
are  as  follows: 

1.  Red  slate,  Matthews   quarry,    Poultney,    Washington   County,  New 

York. 

2.  Red  slate,  Empire  Red  Slate  Company,  Granville,  N.  Y. 

3.  4.   Red  slate,  National  Red  Slate  Company,  Raceville,  N.  Y. 

5.  Green  slate,  National  Red  Slate  Company,  Raceville,  N.  Y. 

6.  Unfading  green  slate,  Eureka  quarries,  Poultney,  Vt. 

7.  Variegated  slate,  Eureka  quarries,  Poultney,  Vt. 

8.  Purple  slate,  Francis  quarry,  Hydeville,  Vt. 

9.  Purple  slate,  McCarthy  quarry,  Lake  St.  Catharine,  Vt. 

10.  Sea-green  slate,  Auld  &  Conger  quarry,  Wells,  Vt. 

11.  Black  slate,  American  Black  Slate  Company,  Benson,  Vt. 

12.  Sea-green  slate,  Hughes  quarry,  Pawlet,  Vt. 

13.  Sea-green  slate,  Griffith  quarry,  South  Poultney,  Vt. 

14.  Sea-green  slate,  Rising  &  Nelson  quarry,  West  Pawlet,  Vt. 

15.  Unfading  green  slate,  Valley  Slate  Quarry  Company,  Poultney,  Vt. 

16.  Slate,  Guilford,  Vt. 

17.  Slate,  Lake  Shore  quarry,  Hydeville,  Vt. 


TABLE  57.  —  ANALYSES  OF  SLATES:   NEW  JERSEY,   PENN- 
SYLVANIA,  MARYLAND. 


1 

2 

3 

4 

5 

6 

7 

8 

9 

Silica.  .  . 

58.37 
21.98 
n.d. 
10.66 
0.30 
1.20 

1.93 

0.11 
0.39 
4.03 

55.88 
21.85 
1.27 
9.03 
0.16 
1.50 
j  3.64 
(  0.46 
0.05 
n.d. 
3.39 

60.32 
23.10 
n.d. 
7.05 

'6^87 
3.83 
0.49 
0.09 
n.d. 
4.08 

56.85 
15.24 
0.84 
5.52 
4.24 
2.93 
2.34 
1.38 
1.72 
3.58 
n.d. 

56.38 
15.27 
0.78 
4.90 
4.23 
2.84 
3.51  ) 
1.30  j 
1.72 
3.67 
4.86 

68.621 
12.681 

n.d.  f 
4.20J 
1.31 
1.80 

3.  73  I 

n.d. 
2.99 
4.47 

90.97 

1.13 
2.48 
n.d. 
n.d. 
n.d. 
n.d. 
n.d. 

90.09 

2.07 
2.57 
n.d. 
n.d. 
n.d. 
n.d. 
n.d. 

89.27 

2.67 
0.93 
n.d. 
n.d. 
n.d. 
n.d. 
n.d. 

Alumina  
Titanic  oxide  .... 
Iron  oxides  
Lime 

Magnesia  
Potash  I 
Soda      J  
Iron  sulphide  .... 
Carbon  dioxide.  . 
Water  

Of  the  above  analyses,  1-3  are  of  slates  from  the  Peachbottom 
district  in  Maryland  and  Pennsylvania;  4-6  are  from  the  Lehigh 
or  Slatington  district  of  Pennsylvania;  and  7-9  are  from  the 
New  Jersey  continuation  of  the  last-mentioned  region. 


SLATES 


105 


1.  Harford  County,  Md.;  Booth,  Garrett  &  Blair,  analysts;  20th  Ann.  Rep. 

U.  S.  Geol.  Sur.,  pt.  6,  p.  399. 

2.  Humphreys  quarry,  Delta,  York  County,  Pa. ;  A.  S.  McCreath,  analyst; 

ibid,  p.  436. 

3.  Lancaster  County,  Pa.     Quoted  by  Merrill,  "  Stones  for  Building  and 

Decoration." 

4.  Washington  vein,  Hazel  Hill  quarry,  Slatington,'Pa. ;  W.  F.  Hillebrand, 

analyst;  Bull.  275,  U.  S.  Geol.  Sur.,  p.  84. 

5.  Lower  Franklin  vein,  old  Franklin  quarry,  Slatington,  Pa.;  ibid,   j 

6.  East  Bangor,  Northampton  County,  Pa.;  H.  Leffman,  analyst;  20th 

Ann.  Rep.  U.  S.  Geol.  Sur.,  pt.  6,  p.  436. 

7.  Springdale,  N.  J.;  Ann.  Rep.  N.  J.  State  Geol.  for  1900,  p.  78. 

8.  Newton,  N.  J.;  Ann.  Rep.  N.  J.  State  Geol.  for  1900,  p.  77. 

9.  Lafayette,  N.  J.;  Ann.  Rep.  N.  J.  State  Geol.  for  1900,  p.  74. 


TABLE  58.  —  ANALYSES  OF  SLATES :  VIRGINIA,  TENNESSEE, 

GEORGIA. 


1 

2 

3 

4 

5 

6 

7 

8 

Silica 

55  58 

56  33 

60  65 

54  76 

58  45 

59  00 

58  20 

57  40 

Alumina  

24.53 

22.26 

16.87 

24.11 

21.88 

23.44 

18.83 

23.65 

Ferric  oxide  

0.11 

5.21 

7.79 

n.d. 

6.04 

6.28 

n.d. 

4.45 

Ferrous  oxide 

8  70 

4  23 

nd 

nd 

nd 

n  d 

5  78 

n  d 

Lime  .  .  . 

0  42 

0  68 

1  91 

n.d. 

1  86 

1  30 

4  35 

3  23 

Magnesia 

1.95 

•1.48 

2  39 

n.d. 

0  46 

0  50 

3  51 

3  23 

Potash 

3  17 

3  58 

3  80 

n  d 

1  60 

2  04 

2  51 

n  d 

Soda  

1.71 

1.49 

2.18 

n.d. 

2.34 

1.78 

0.69 

n.d. 

Sulphur  

0.008 

0.004 

0.69 

n.d. 

0.65 

0.23 

0.49 

n.d. 

Carbon  dioxide  .... 

1.99 

1.69 

n.d. 

n.d. 

n.d. 

n.d. 

0.60) 

Combined  water  .  .  . 

3.39 

2.86 

3.63 

n.d. 

6.66 

4.64 

4.07} 

.80 

1.  Green  slate,  Standard  Slate  Company,   Esmont,   Albemarle  County, 

Va.;  sampled  by  E.  C.  Eckel,  analyzed  by  Lehigh  Valley  Testing 
Laboratory. 

2.  Black  slate,  same  quarry,  sampler,  and  analyst  as  preceding. 

3.  Gray    slate,    Williams    quarry,    Arvonia,    Buckingham   County,   Va. ; 

H.  Froehling,  analyst;  20th  Ann.  Rep.  U.  S.  Geol.  Sur.,  pt.  6,  p.  458. 

4.  Slate,  near  Warrenton,  Fauquier  County,  Va. 

5.  6.   Slate  from    quarry  Southern    Slate    Company,    Maryville,   Blount 

County,  Tenn.;  analyzed  by  G.  McCulloch;  quoted  in  Bull.   275, 
U.  S.  Geol.  Sur.,  p.  88. 

7.  Slate,  Georgia  Slate  Company,  Rockmart,  Polk  County,  Ga.;  Slocum 

&  VanDeventer,  analysts;  20th  Ann.  Rep.  U.  S.  Geol.  Sur.,  pt.  6, 
p.  376. 

8.  Slate,  Southern  States  Portland  Cement  Company;  J.  F.  Davis,  analyst; 

Bull.  275,  U.  S.  Geol.  Sur.,  p.  60. 


106 


BUILDING  STONES  AND   CLAYS 


TABLE  59.  —  ANALYSES  OF  SLATES  :  ARKANSAS. 


l 

2 

3 

4 

5 

6 

7 

8 

9 

10 

Silica    

53.81 
25.40 
6.17 
2.75 
0.31 
1.74 
4.27 
0.49 

4.62 
0.66 

54.83 
23.53 
5.06 
3.41 
0.28 
3.05 
3.21 
0.21 

6.01 
0.43 

68.90 
14.03 

'4.'65 
0.37 
1.11 
2.14 
0.05 

7.69 
0.66 

57.79 
22.92 
5.19 
2.62 
0.23 
1.97 
4.66 
0.12 

4.13 
0.48 

69.76 
14.16 

'4.'  58 
0.38 
1.32 
1.94 
0.13 

7.44 
0.54 

52.50 
26.31 
3.98 
5.34 
0.28 
2.27 
3.32 
0.04 

5.33 
0.47 

55.71 
25.20 
2.46 
3.97 
0.26 
1.74 
4.51 
0.22 

5.13 
0.53 

53.23 
26.29 
3.81 
4.21 
0.31 
1.87 
3.58 
tr. 

5.82 
0.59 

52.35 
26.16 
5.81 
3.16 
0.29 
2.29 
3.82 
0.16 

5.19 
0.57 

52.79 
24.96 
6.27 
3.81 
0.28 
1.69 
3.52 
0.03 

5.79 
0.72 

Alumina  

Ferric  oxide  
Ferrous  oxide  
Lime 

Magnesia  

Potash  

Soda 

Carbon  dioxide     ) 
Combined  water  > 
Organic  matter    ) 
Moisture  

11 

12 

13 

14 

15 

16 

17 

Silica  (SiO2)  . 

66  16 

68  79 

69  04 

69  07 

67  90 

64  00 

63  22 

Alumina  (Al2Oa)  .  .    . 

8  62 

14  26 

12  66 

11  40 

10  42 

11  59 

16  76 

Ferric  oxide  (Fe2O3)  
Ferrous  oxide  (FeO)  

9.04 
3  44 

5.90 
1.16 

8.55 
1.30 

7.66 
1.04 

6.22 

13.71 

9.54 

Lime  (CaO)  

1.77 

1.40 

1.75 

1.56 

3.17 

1.56 

1  75 

Magnesia  (MgO)  
Potash  (K2O) 

.78 
4  96 

1.43 
3.09 

1.87 
2.98 

3.14 

3.88 

4.34 
4  11 

2.03 
1  36 

1.52 
1  43 

Soda  (Na2O)  

.64 

.09 

.09 

.96 

69 

64 

07 

Sulphur  in  SO3  
Sulphur  in  FeS2  
Carbon  (C)  

.08 
.02 
2.10 

.44 
.01 
2.01 

.06 
.01 
tr. 

.02 
.01 

.06 
.01 

1.78 

.05 
.04 
4.03 

.05 
.03 
3.70 

Carbon  dioxide  (CO2)  
Water       .                          .    . 

.09 

.18 

.11 

.47 

.72 

.84 

.11 
.24 

.01 
.23 

.01 

57 

.01 
1  01 

Analyses  1-10  inclusive  of  the  preceding  table  were  made  at 
a  laboratory  formerly  maintained  in  St.  Louis  by  one  branch 
of  the  United  States  Geological  Survey,  but  not  manned  by 
Survey  chemists.  The  analyses  are  quoted  from  Bulletin  430, 
United  States  Geological  Survey,  page  334,  and  are  repeated 
here  for  what  they  may  be  worth.  In  the  writer's  opinion  they 
are  as  doubtful  as  those  formerly  turned  out  at  the  Watertown 
Arsenal. 

Analyses  11-17  are  quoted  from  Bulletin  275,  United  States 
Geological  Survey,  page  53,  where  they  are  credited  to  W.  G. 
Waring.  In  this  set  the  alumina  is  as  remarkably  low  as  it  was 
high  in  the  other  series.  Taken  together  the  two  sets,  which 
cover  much  the  same  slates,  are  excellent  examples  of  what  may 


SLATES 


107 


be  expected  when  difficult  analyses  are  turned  over  to  ordinary 
chemical  laboratories.     The  localities  are  as  follows: 

1,  4.   Red  slate,  Southwestern  Slate  Company. 

2,  Green  slate,  Southwestern  Slate  Company. 

3,  5.   Black  slate,  Harrington  property. 
6,  7.   Green  slate,  Jones  property. 

8,  9.   Red  slate,  Jones  property. 

10.  Buff  slate,  Baker  property. 

11.  Green  slate,  Southwestern  Slate  Company. 

12.  Red  slate,  Southwestern  Slate  Company. 

13.  14.   Red  slate,  State  House  Cove. 

15.  Green  slate,  State  House  Cove. 

16,  17.   Black  slate,  Crooked  Creek. 

TABLE  60.  —  ANALYSES  OF  SLATES  :  CALIFORNIA,  UTAH. 


1 

2 

3 

4 

Silica               

63.52 

47.30 

45  15 

54  05 

Alumina           

16.34 

15.53 

16  33 

20  95 

Iron  oxides  

6.79 

8.00 

8.42 

9  28 

LJrne              

0.98 

7.83 

6.42 

0  22 

Magnesia       

2.50 

7.86 

8.72 

0  12 

Potash  and  soda  

n.d. 

3.17 

n.d. 

n.d 

Water,  carbon  dioxide  

4.86 

9.92 

11.28 

3  90 

1.  Black  slate,  sedimentary;  Eureka  Slate  Company,  Kelsey,  El  Dorado 

County,  Cal.;  sampled  by  E.  C.  Eckel;  analyzed  by  W.  T.  Schaller. 

2.  Green  slate,  igneous;  same  quarry  as  preceding;  analysis  quoted  by 

company. 

3.  Green  slate,  igneous;  same  quarry  as  preceding;  sampled  by  E.  C. 

Eckel;  analyzed  by  W.  T.  Schaller. 

4.  Purple  slate,  near  Provo,  Utah;  sampled  by  E.  C.  Eckel;  analyzed  by 

W.  T.  Schaller. 


TABLE  61.  — ANALYSES  OF  EUROPEAN  ROOFING  SLATES. 


1 

2 

3 

4 

5 

6 

7 

8 

9 

10 

11 

12 

13 

•Silica  (SiO2)  

55.06 

58.30 

50.88 

55.8 

59.3 

60.50 

60.68 

61.43 

61.57 

65.63 

48.60 

59  35 

67.56 

Alumina  (A12O3)  

22  55 

21.89 

14.12 

25.7 

17.5 

19.70 

21.20 

19  10 

19  22 

20  20 

23.50 

18  56 

12.23 

Ferric  oxide  (FejOa)  .  .  . 

1.97 

7.05 

0.3 

2.3 

7.83 

5.68 

4.81 

6.63 

2.72 

11.30 

1  10 

2  87 

Ferrous  oxide  (FeO)  .  .  . 

5.96 

2.57 

9.96 

9.5 

3.8 

0  46 

3  12 

1  20 

0  85 

4  75 

6.99 

Lime  (CaO)  

1.30 

0.39 

8.72 

4.4 

5.0 

1.12 

1.71 

0.31 

0.22 

0.19 

5  20 

0  27 

Magnesia  (MgO)  
Soda  (Na20)  

2.92 
2  17 

1.09 
1  18 

8.67 

tr. 

2.20 
2  20 

0.88 
?,  09 

2.29 
0.83 

0.93 
3.63 

0.71 
3.81 

1.60 

3.60 
(1  48 

3.03 
1.28 

Potash  (K2O)  

3.82 

2.45 

0.88 

3.18 

3  64 

3.24 

1  4.  70 

11  77 

1  76 

Carbon  dioxide  (CO2)  .  . 

6.47 

3.2 

2.4 

4.45 

Water  

4.35 

4.ei 

0.2 

6.0 

3.30 

2.88 

3.52 

3.25 

3.17 

7.60 

3.41 

1.00 

108  BUILDING  STONES  AND  CLAYS 

1.  Mohradorf,  Austria;  Nikolic,  analyst;  19th  Ann.  Rep.  U.  S.  Geol.  Sur., 

pt.  3,  p.  261. 

2.  Delabole,  Cornwall,  England;  J.  A.  Phillips,  analyst;  19th  Ann.  Rep. 

U.  S.  Geol.  Sur.,  pt.  3,  p.  261. 

3.  Lake  District,  Westmoreland,  England;  G.  Vogt,  analyst;  Jour.  Inst. 

British  Architects,  Vol.  3,  p.  196. 

4.  5.   Lake  district,  Westmoreland,  England;   Lock,  analyst;  Economic 

Mining,  p.  367. 

6.  Average,  Wales;  Hull,  "  Building  Stones,"  p.  291. 

7.  Llanberis,  Wales;  19th  Ann.  Rep.  U.  S.  Geol.  Sur.,  pt.  3,  p.  261. 

8.  Rimogne,    Ardennes,    France;    Klement,    analyst;     19th   Ann.    Rep. 

U.  S.  Geol.  Sur.,  pt.  3,  p.  261. 

9.  10.   Fumay,  Ardennes,  France;   A.  Renard,  analyst;   19th  Ann.  Rep. 

U.  S.  Geol.  Sur.,  pt.  3,  p.  261. 

11.  Angers,  France;  D'Aubisson,  analyst. 

12.  Frankenberg,   Prussia;  A.  von  Groddeck,  analyst;    19th  Ann.   Rep. 

U.S.  Geol.  Sur.,  pt.  3,  p.  261. 

13.  Westphalia,  Prussia;  H.  von  Decken,  analyst;  19th  Ann.  Rep.  U.  S. 

Geol.  Sur.,  pt.  3,  p.  261. 


COLOR,  TEXTURE  AND  STRUCTURE. 

Color  of  Slates.  —  Slates  from  various  districts,  and  in  some 
cases  even  from  different  parts  of  the  same  quarry,  show  very 
marked  differences  in  color.  The  commonest  colors  are  various 
shades  of  gray  and  bluish  gray.  Black  is  probably  the  next 
most  abundant  color,  followed  in  turn  by  reds  of  various  shades. 
Greens  are  less  common,  especially  the  purer  and  clearer  greens, 
though  grayish  green  is  not  rare.  Purple  is  perhaps  the  scarcest 
of  the  colors  in  which  slate  is  found.  Yellow,  brown  and  buff 
slates  occur,  but  these  colors  are  invariably  due  to  weathering 
and  though  showing  at  the  surface  do  not  occur  in  the  merchant- 
able slate. 

In  almost  all  cases,  the  colors  shown  by  slates  are  due  to  the 
amount  and  condition  of  two  of  the  constituents  of  the  slate  — 
organic  matter  and  iron  oxides.  It  may  be  fairly  assumed  that 
the  normal  or  average  slate  color  is  some  shade  of  gray.  If  the 
slate  contains  considerable  finely  divided  carbonaceous  matter, 
it  will  probably  show  a  glossy  black  color  on  its  cleavage  surfaces. 
If  it  is  high  in  ferric  iron,  it  will  probably  be  a  red  or  purple  slate. 
If  the  iron  is  in  the  ferrous  form,  the  slate  will  normally  be  green, 
if  fairly  free  from  organic  matter;  and  black  if  organic  carbon  is 
present  in  addition  to  the  ferrous  iron. 


SLATES  109 

Economic  Importance  of  Color.  —  The  color  of  slate  is  of  im- 
portance industrially  in  so  far  as  it  affects  the  physical  properties, 
the  permanence  and  the  salability  of  the  product. 

So  far  as  strength  is  concerned,  there  is  little  to  choose  between 
the  various  colors.  The  glossy  black  slates  are,  on  the  average, 
apt  to  be  somewhat  finer  grained,  somewhat  softer,  and  con- 
siderably more  smooth  and  even  grained  than  those  of  any  other 
color.  The  gray  slates,  on  the  other  hand,  usually  are  at  the 
other  extreme  of  the  series  in  all  of  these  respects;  while  the  red 
and  green  slates  are  intermediate.  The  properties  in  which  the 
black  slates  excel  are  obviously  those  which  fit  them  well  for 
mill  stock;  while  they  are  negative  or  actually  harmful  so  far 
as  strength  and  durability  are  concerned. 

In  regard  to  permanence  of  color  throughout  long  exposure  to 
the  weather,  which  is  a  matter  of  importance  in  the  selection  of 
roofing  slates,  slates  may  be  either  practically  permanent  in  tint, 
they  may  fade  evenly  and  slightly  or  they  may  fade  or  discolor 
in  uneven  patches.  Except  for  the  difficulty  in  matching  the 
tint  when  a  few  slates  on  a  roof  require  replacement,  there  would 
be  no  objection  to  a  moderate  and  even  fading,  while  of  course 
a  slate  which  changes  color  in  blotches  is  highly  objectionable. 
So  far  as  original  color  affects  these  matters,  it  may  be  said  that 
the  black  and  gray  slates  are  commonly  either  entirely  permanent 
in  color,  or  show  but  slight  changes;  that  the  bluish  slates  often 
turn  more  grayish,  while  most  red  slates  take  on  a  browner  tint. 
The  green  slates  are  the  most  doubtful  always,  for  while  some  of 
them  are  practically  permanent  in  color,  others  discolor  badly. 
The  change  in  color  of  the  fading  green  slates  is  due,  according 
to  Dale  and  Hillebrand,  to  the  presence  of  small  quantities  of 
unstable  iron-lime-magnesia  carbonates,  in  which  the  ferrous 
iron  gradually  oxidizes  and  hydrates  to  limonite.  The  develop- 
ment of  discoloring  blotches  in  slate  of  any  tint  is  generally  due 
either  to  the  same  cause,  or  to  the  weathering  of  small  grains  of 
iron  sulphide  (pyrite  or  marcasite). 

The  salability  of  slate  is  largely  influenced  by  color.  As  the 
entire  slate  trade  is  governed  by  tradition,  it  being  in  this  respect 
perhaps  the  most  archaic  of  existing  industries,  it  is  very  difficult 
to  introduce  a  new  slate,  and  particularly  so  if  its  color  differs 
from  that  to  which  the  particular  local  market  is  accustomed. 
When  a  new  company  attempts  to  do  this,  its  competitors  never 


110  BUILDING  STONES  AND  CLAYS 

have  the  slightest  difficulty  in  producing  a  hundred  ancient 
Welshmen  who  are  willing  to  swear  that,  in  all  the  years  since 
Wales  first  rose  above  the  sea,  no  one  has  appeared  mad  enough 
to  even  suggest  using  a  slate  of  that  particular  tint  for  roofing 
purposes.  It  is  only  recently  that  the  slate  trade  has  thought  of 
submitting  such  matters  to  laboratory  tests,  in  place  of  relying 
on  the  traditional  lore  of  the  bards. 

There  is  a  very  definite  advantage  to  a  slate  company  arising 
from  the  control  of  two  or  more  colors  of  slate,  whether  these 
are  taken  from  the  same  quarry  or  from  entirely  different  dis- 
tricts. Architects  usually  specify  color  as  well  as  grade,  and  a 
company  which  can  supply  only  one  good  color  or  type  of  slate 
must  necessarily  lose  a  good  deal  of  desirable  business.  A  good 
example  of  the  advantage  of  controlling  two  well-contrasting 
colors  is  afforded  by  a  western  company  whose  quarry  is  in  a 
glossy  black  slate,  but  with  a  few  narrow  bands  of  green  slate. 
The  latter  is  marketed  for  lettering  and  ornamental  work  on  the 
black  slate  background,  and  the  idea  has  taken  very  satisfac- 
torily. In  the  eastern  states  the  slate  industry  seems  to  be  on 
the  verge  of  developing  on  a  larger  scale  than  heretofore,  and 
doubtless  this  development  will  ultimately  take  the  form  of 
large  companies  each  owning  a  number  of  quarries  in  different 
districts,  so  that  each  can  supply  slate  of  any  specified  grade 
and  color. 

Cleavage.  —  The  most  striking  difference  between  slates  and 
shales  lies  in  the  fact  that  while  shales  ordinarily  break  into 
irregular  blocks,  slates  show  a  very  perfect  cleavage  in  one  plane, 
though  breaking  irregularly  in  all  other  directions.  This  slaty 
cleavage  is  a  phenomenon  closely  akin  to  the  gneissoid  lamination 
shown  by  many  granites,  and  discussed  on  an  earlier  page.  In 
neither  case  is  the  cleavage  nor  banding  necessarily  parallel  to 
earlier  bedding  planes.  In  slates,  for  example,  it  is  occasionally 
found  that  the  cleavage  plane  intersects  the  original  bedding 
plane  at  a  high  angle;  and  indeed  most  books  dealing  with  the 
subject  allow  it  to  be  supposed  that  such  discordance  between 
cleavage  and  bedding  is  the  normal  condition.  The  writer's 
experience,  however,  is  that  in  by  far  the  majority  of  cases  the 
cleavage  of  our  commercial  slates  is  either  absolutely  parallel 
to  the  original  bedding,  or  else  diverges  from  it  at  only  a  small 
angle. 


SLATES  111 

When  the  bedding  plane  and  plane  of  slaty  cleavage  coincide 
exactly,  so  that  the  slate  splits  most  readily  along  its  original 
bedding  planes,  the  split  surface  will  usually  be  rough  and  un- 
even, so  that  such  a  slate  does  not  give  satisfactory  roofing 
material  but  must  be  used  as  mill  stock. 

Surface  weathering  decreases  the  durability  and  the  splitting 
properties  of  slates.  For  this  reason  it  is  difficult  to  decide  as 
to  the  value  of  a  slate  property  from  surface  exposures  only.  It 
may  be  taken  as  a  general  rule  that  the  deeper  from  the  surface, 
the  better  the  slates  will  be  as  to  soundness,  strength,  color, 
cleavage  and  size  of  blocks.  This  rule  is  not  invariable,  however, 
and  it  cannot  be  carried  too  far.  Slate  from  an  opening  50  feet 
below  the  surface  will  almost  always  be  superior  in  every  way 
to  surface  slate;  but  slate  from  a  100-foot  hole  should  not  be 
expected  to  be  much  if  any  better  than  that  from  a  50-foot  hole. 

PHYSICAL  PROPERTIES  AND   TESTING. 

Desirable  Properties  of  Slates.  —  Slate  may  be  used  for  two 
general  purposes  —  mill  stock  and  roofing  slate;  and  the  prop- 
erties which  are  desirable  for  one  use  are  not  necessarily  im- 
portant for  the  other,  a  fact  which  is  often  overlooked. 

For  mill  stock  a  slate  should  preferably  be  fine  and  even- 
grained,  soft  rather  than  hard  and  reasonably  uniform  in  color. 
For  the  sake  of  the  dressing  machinery  it  should  be  free  from 
grains  of  quartz,  pyrite  or  other  hard  minerals.  Its  color  and 
chemical  composition  are  of  no  particular  importance  for  such 
use. 

For  roofing  slate  durability  and  strength  are  of  value.  A  roof- 
ing slate  should  be  practically  permanent  in  color,  even  after 
exposure  to  damp  and  acid  atmospheres;  it  should  stand  punch- 
ing cleanly,  and  should  be  strong  and  tough  enough  to  stand 
rough  handling  during  shipment,  laying  and  use.  Pyrite,  iron 
carbonate  and  other  unstable  minerals  are  highly  undesirable. 

It  will  be  seen  from  the  above  summary  that  no  one  is  par- 
ticularly interested  in  the  compressive  strength  of  roofing  slate 
—  and  still  this  is  occasionally  determined  and  recorded  with 
proper  solemnity.  The  specific  gravity  is  of  interest  chiefly 
because  a  dense  heavy  slate  may  be  expected,  other  things  being 
equal,  to  be  more  durable  than  one  of  more  porous  nature. 


112 


BUILDING  STONES  AND  CLAYS 


TABLE  62.  —  SPECIFIC  GRAVITY  OF  ROOFING  SLATES. 


Quarry. 

Location. 

Tested  by 

Specific 
gravity. 

Eureka  quarries 

Poultney  Vt 

W  F  Hillebrand 

Eureka  quarries  

Poultney,  Vt. 

W  F  Hillebrand 

2  onto 

Hughes  quarry  

Pawlet,  Vt. 

W  F  Hillebrand 

27Q1 

Auld  &  Conger  

Wells,  Vt  

W  F  Hillebrand 

2  7627 

McCarty  quarry  
American  Black  Slate  Co  
American  Black  Slate  Co  
American  Black  Slate  Co.  . 

South  Poultney,  Vt  
Benson,  Vt  
Benson,  Vt  
Benson,  Vt 

W.  F.  Hillebrand.  . 
W.  F.  Hillebrand.. 
W.  C.  Day  
W  C  Day 

2.8064 
2.7748 
2.764 
2  786 

National  Red  Slate  Co  

Raceville,  Washington  Co.,  N.  Y. 

2  7839 

National  Red  Slate  Co  

Raceville,  Washington  Co.,  N.  Y. 

2  7171 

Empire  Red  Slate  Co  

Granville,  Washington  Co.,  N.  Y. 

2  8085 

Peach  Bottom,  Pa.-Md.*  
Chapman,  Pa  
Albion,  Pa.*  
Bangor,  Pa.*  
Westmoreland,  England  

M.  Merriman  
E.  S.  Bailey  
M.  Merriman  
M.  Merriman  
G.  Vogt. 

2.894 
2.79 
2.775 
2.780 
2  77 

Delabole,  Cornwall,  England.  .  . 
Mohradorf,  Austria,  Silesia  

Lake  District,  England  

J.A.Phillips  
Nikolic  

2.81 
2.78 
(2.775 

(2.8 

Average  of  12  specimens. 


TABLE  63.  —  COMPARATIVE  TESTS  OF  ROOFING  SLATES. 

(MERRIMAN.) 


1       o> 

•S»8 

«  >>_. 

^_ 

iff 

l!| 

Q 

a 

ills 

III 

fl.s 

Locality. 

Color. 

f*si| 

'  gS| 

"1 

c«  g^S  g 

fcjj 

Hie 

13  '55  3  s 

ft! 

I'll* 

|B 

ill! 

||.s 

|sl 

Epl 

1 

i|» 

I* 

5|'§ 

Maine  district: 

Merrill  Slate  Co.,  Brownville. 

Gray  

9,880 

0.200 

2.798 

0.265 

0.148 

0.305 

Monson     Consol,     Slate    Co., 

Monson  

Gray  

9,130 

0.205 

2.794 

0.256 

0.188 

0.286 

New  York-  Vermont  district: 

Matthews  Slate  Co.,  Granville 

Green... 

8,050 

0.190 

2.783 

0.226 

0.374 

0.379 

Matthews  Slate  Co.,  Granville 

Red  

9,220 

0.232 

2.848 

0.148 

0.243 

0.373 

Vermont  Green  Slate  Co  

Green  

6,410 

0.225 

2.771 

0.341 

0.231 

0.295 

Rising  &  Nelson  

Green  

7,250 

0.207 

2.736 

0.190 

0.325 

0.768 

Lehigh  district:  Penn.-N.  J. 

Chapman  Slate  Co.,  Chapman, 

Pa  

Dark  gray 

9,460 

0.212 

2.764 

0.208 

0.231 

0.383 

Albion  quarry,  Pan  Argyle  
Old  Bangor  quarry,  Bangor 

7,150 
9,810 

0.270 
0.312 

2.775 
2.780 

0.238 
0.145 

0.547 
0.446 

Peachbottom  district:  Penn.-Md. 

Locality  not  stated 

11,260 

0.293 

2.894 

0.224 

0.226 

Virginia  district: 
Williams  Slate  Co.,  Arvonia  .  . 

Dark  gray 

9,040 

0.227 

2.781 

0.060 

0.143 

0.394 

Pitts  quarry,  Arvonia  

Dark  gray 

9,850 

0.225 

2.791 

0.108 

0.216 

0.323 

List  of  References  on  Properties  and  Testing  of  Slates.  —  The 
following  brief  list  will  serve  to  direct  the  reader's  attention  to 


SLATES  113 

the  only  papers  on  this  subject  which  seem  to  contain  matter  of 
serious  importance. 

Dale,  T.  N.     Slate  deposits  and  slate  industry  of  the  United  States. 

Bui.  275,  U.  S.  Geol.  Sur.,  pp.  45-50,  122-125,  on  tests  of  slate. 
Merriman,  M.     The  strength  and  weathering  qualities  of  roofing  slates, 

Trans.  Amer.  Soc.  Civil  Engineers,  Vol.  XXVII,  pp.  331-349.     1892. 
Merriman,  M.     The  strength  and  weathering  qualities  of  roofing  slates, 

Trans.  Am.  Soc.  C.  E.,  Vol.  XXXII,  pp.  529-543.     1894. 
Merriman,  M.     Recent  tests  of  various  roofing  slates.     Bull.  275,  U.  S. 

Geol.  Sur.,  pp.  122-124.     1906. 

DISTRIBUTION  AND   PRODUCTION   OF  SLATE. 

Geologic  Distribution  of  Slates.  —  The  formation  of  a  deposit 
of  roofing  slate,  as  has  been  explained  in  previous  sections,  in- 
volves the  existence  of  clayey  sediments  in  an  area  which  under- 
goes extreme  metamorphism.  The  geologic  age  of  the  original 
clay  beds  does  not  enter  into  the  problem,  except  that  as  a 
general  thing  the  older  beds,  having  a  longer  history,  have  had 
more  chance  of  being  metamorphosed.  But  unless  the  inquiry 
be  limited  to  particular  geographic  or  geologic  areas,  it  is  not  pos- 
sible to  say  in  advance  that  the  rocks  of  any  particular  geologic 
period  are  likely  to  be  slate-bearing. 

If,  however,  the  question  is  so  limited  to  particular  areas, 
geologic  history  will  afford  some  guidance  in  the  search  for  slate. 
In  the  eastern  and  southeastern  United  States,  for  example,  all 
of  the  known  slate  deposits  are  of  either  Cambrian  or  Ordovician 
age;  because  in  the  New  England  and  Appalachian  region  these 
rocks  were  involved  in  the  general  metamorphism  of  the  region 
while  the  Carboniferous  and  newer  rocks  were  deposited  after 
the  bulk  of  the  metamorphic  action  had  ceased  in  this  area.  In 
the  western  states,  on  the  other  hand,  where  earth  movements 
of  great  intensity  took  place  much  later  in  geologic  history,  we 
find  clayey  sediments  of  Jurassic  age  converted  into  slate.  The 
slates  of  the  Lake  Superior  region,  in  Michigan  and  Minnesota, 
are  even  older  than  those  of  the  eastern  states,  for  all  of  the 
Lake  Superior  slates  date  back  to  pre-Cambrian  time. 

Geographic  Distribution  of  Slates.  —  The  geographic  distri- 
bution of  slate  deposits  in  the  United  States,  as  may  be  inferred 
from  the  preceding  section,  is  fixed  by  the  geologic  history  of 
the  various  portions  of  the  country.  Wherever  clayey  sediments 
have  existed  in  any  region,  during  a  period  when  the  region  in 


114  BUILDING  STONES  AND  CLAYS 

question  was  subjected  to  metamorphic  action,  we  may  fairly 
expect  to  find  that  in  part  of  their  extent  at  least  these  clayey 
sediments  have  been  converted  into  slates.  Since  the  physical 
results  of  earth  movements  are  most  extreme  in  cases  where 
relatively  soft  rocks  are  pressed  against  or  between  masses  of 
harder  rocks,  it  is  natural  enough  to  find  that  slaty  cleavage  is 
best  developed  under  these  conditions.  Accordingly,  practically 
all  of  the  important  slate  deposits  occur  in  areas  where  clayey 
sediments  had  been  deposited  along  an  older  granite  shore  line; 
and  where  these  sediments  were  later  pressed  against  the  less 
yielding  granites  and  gneisses.  In  New  England  and  the  Appa- 
lachian region  the  clayey  sediments  were  deposited  during  the 
Cambrian  and  Ordovician  periods  along  a  shore  line  of  pre- 
Cambrian  gneisses  and  schists;  and  during  subsequent  earth 
movements  many  of  the  sediments  were  turned  into  slates.  In 
the  Lake  Superior,  Ozark  and  Rocky  Mountain  regions  a  similar 
sequence  of  events  took  place,  though  not  at  the  same  periods 
in  the  earth's  history.  The  geologic  history  of  slate  deposits 
therefore  limits  their  possible  geographic  distribution,  so  that 
we  find  all  of  the  important  slate  deposits  of  the  world  fringing 
older  igneous  masses. 

Chief  American  Quarry  Districts.  —  For  local  details  concern- 
ing the  various  slate  deposits  of  the  United  States,  reference 
should  be  made  to  the  official  report  by  Dale  and  others  noted 
in  the  bibliography  on  page  125  of  this  volume.  In  the  present 
place  only  brief  mention  will  be  made  of  the  more  important 
American  slate  districts.  The  map  accompanying  Dale's  report 
shows  the  location  of  the  present  producing  districts,  as  well  as 
of  a  number  of  the  more  promising  prospects. 

For  a  reason  suggested  in  the  previous  section,  the  American 
slate  districts  follow  in  their  general  distribution  the  granite  areas. 
We  have,  therefore: 

1.  Extensive  slate  deposits  along  the  Appalachian  belt,  from 
New  England  to  Alabama.  In  this  region  the  slates  are  all  of 
Cambrian  or  Ordovician  age,  and  represent  original  clayey  beds 
which  were  violently  stressed  against  and  between  the  older  and 
more  resistant  masses  of  pre-Cambrian  granites,  gneisses  and 
schists.  The  principal  producing  areas  within  this  extensive 
general  belt  are  the  isolated  Monson  district  of  Maine;  the  im- 
portant area  along  the  New  York- Vermont  border;  the  Lehigh 


SLATES  115 

region  of  Pennsylvania-New  Jersey;  the  Peachbottom  region  of 
Pennsylvania-Maryland;  the  separated  Esmont,  Arvonia  and 
Snowden  areas  of  Virginia;  and  less  well-developed  areas  in 
eastern  Tennessee  and  northwest  Georgia. 

2.  Extensive  but  little  developed  slate  deposits  bordering  the 
massive  rocks  of  the  Lake  Superior  region,  in  Minnesota  and 
Michigan. 

3.  Separated  small  areas  in  Texas  and  Arkansas,   fringing 
regions  of  great  local  earth  movement. 

4.  Scattered  and  mostly  undeveloped  areas  along  the  Rocky 
Mountain  and  other  western  mountain  chains;  the  only  developed 
district  being  in  central  California. 

Chief  Foreign  Districts. — British  slates  are  obtained  principally 
from  three  districts:  North  Wales,  Cornwall  and  Westmoreland. 
The  Welsh  slates  are  green,  purple,  black  and  pale  gray  in  color;  are 
quarried  largely  near  Llanberris,  Penrhyn,  Ffestiniog,  Llangollen, 
Carnarvon  and  Bangor;  and  are  shipped  from  Portmadoc  and 
other  ports.  The  Cornish  slates  are  gray  to  bliie'  nr  cdlbr,  are 
quarried  at  Delabole  and  shipped  from  Tintagel  and  Boscastle. 
The  slates  of  the  Lake  district  of  Westmoreland  are  light  blue 
to  light  green  in  color,  are  quarried  near  Kendal  and  are  rarely 
exported.  Other  districts  in  England,  as  well  as  in  Ireland  and 
Scotland,  produce  smaller  amounts  of  slate. 

The  principal  slate  deposits  of  France  are  located  in  two  quite 
distinct  districts,  one  being  near  Angers  in  the  Department  of 
Maine  et  Loire  and  the  other  in  the  Ardennes.  The  slates 
quarried  in  the  first  district,  at  Angers  and  Poligny,  are  dark 
blue  in  color  and  are  shipped  from  Nantes.  The  Ardennes  slates 
are  quarried  at  Rimogne,  Fumay  and  Deville. 

Dressing  of  Roofing  Slates.  —  Roofing  slates  pass  through' 
three  operations  —  blockmaking,  splitting  and  dressing  —  be-1 
fore  they  are  ready  for  the  market.  At  times  they  are  further! 
subjected  to  punching  or  to  counter-sinking,  according  to  the 
requirements  of  the  purchaser.  All  of  these  operations  were  for- 
merly carried  on  by  hand,  and  at  most  small  quarries  and  some 
large  ones  hand  labor  is  still  depended  on  for  most  of  the  work. 
Some  of  the  operations  can,  however,  be  done  more  economically1 
by  machinery. 

The  slate  is  hoisted  from  the  quarry  in  slabs  which  average 
perhaps  6  feet  by  3  feet  by  1J  feet.  When  hand  dressing  is. 


Fig.  17. —  Slate  dressing:  the  dressing  sheds. 


[116]  Fig.  18.  —  Slate  dressing:  the  beginning  of  sculping. 


SLATES 


117 


depended  on,  these  slabs  are  loaded  on  a  tram  car  and  pushed  to 
the  dressing  sheds,  a  series  of  little  sheds  or  cabins  each  occupied 
by  a  dressing  gang.  A  dressing  gang  includes  three  men  — 
a  blockmaker,  a  splitter  and  a  dresser.  Ordinarily  each  gang 
takes  contracts  from  the  company  at  a  fixed  price  per  square  of 
finished  slate,  the  receipts  being  divided  by  the  three  members 
of  the  gang  in  fairly  equal  proportions,  though  the  dresser  or 


Fig.  19.  —  Slate  dressing:  sculping.        , 

trimmer  usually  gets  a  little  less  than  the  other  two.  The  work 
is  divided  and  carried  on  as  follows:  The  blockmaker  takes  the 
large  slabs  or  blocks  above  noted  and  cuts  them  into  manageable 
slabs  about  2  feet  by  1J  feet  in  size  and  2  inches  thick.  This 
is  done  with  the  chisel.  In  making  the  cut  across  the  grain  the 
operation  is  called  " sculping,"  and  is  shown  in  Figs.  18  and  19. 
A  F-shaped  notch  is  first  cut  in  one  side  of  the  slab  with  the 
gouge  (Fig.  18),  after  which  the  splitting  chisel  is  held  with 
edge  vertical  in  this  notch  and  struck  with  the  hammer  (Fig.  19). 
The  slab  is  now  passed  on  to  the  splitter,  whose  special  tool 


118  BUILDING  STONES  AND   CLAYS 

is  the  thin  splitting  chisel  (Fig.  20),  10  to  15  inches  long,  and 
with  an  edge  2  to  3J  broad.  One  or  more  of  these  are  driven 
into  the  slate,  along  some  cleavage  plane,  with  the  maul,  and 
are  then  worked  backward  and  forward  by  hand  until  the  slate 
splits.  The  splitting  is  continued  until  the  slates  are  reduced 
to  the  proper  thickness,  which  may  be  from  one-eighth  to  one- 
fourth  inch.  The  slates,  now  of  proper  and  uniform  thickness, 


Fig.  20.  —  Slate  dressing:  splitting. 

but  of  irregular  shapes,  are  given  to  the  dresser  or  trimmer, 
who  formerly  trimmed  them  to  size  with  a  knife.  At  present 
hand-  or  foot-power  dressing  machines  are  employed  every- 
where —  the  general  design  being  a  long  knife,  set  vertically  and 
hinged  at  one  end,  while  the  other  end  is  alternately  raised  and 
lowered  by  hand  or  by  a  treadle. 

At  a  large  Pennsylvania  quarry  the  slate  blocks  were  delivered 
by  the  company  in  front  of  the  dressing  sheds,  and  tools  were 
furnished  and  sharpened  at  company  expense,  while  the  dressing 
gang  received  the  following  prices  per  square  of  finished  slate : 


SLATES 


119 


No.  1  quality $1.10  per  square 

Intermediate  quality 1.00  per  square 

No.  2  quality 90  per  square 

It  has  been  noted  that  machine  work  is  now  employed  for  some 
of  these  operations.  Splitting  is  still  done  by  hand  labor,  as1, 
mechanical  splitters  have  rarely  given  good  results.  The  blocks,, 
however,  are  usually  given  at  least  one  sawed  edge  before  being, 
handed  to  the  splitter,  this  being  done  on  a  sawing  table  with 
vertical  saw,  such  as  is  used  in  preparing  mill  stock. 

Measurement  of  Roofing  Slates.  —  Two  different  units  of 
measurement  are  employed  in  the  slate  trade,  the  square  and  the 
mille,  the  former  being  used  at  all  American  quarries,  while  the 
latter  is  found  in  French  and  English  markets. 


—iflr 


LJ_LJ_I_LJ 


Fig.  21.  —  Laying  of  roofing  slate. 

The  square  is  the  number  of  slates  of  a  given  size  necessary  to 
cover  100  square  feet  of  roof,  with  a  given  lap.  Let  b  equal 
breadth  of  slates,  d  equal  length  of  slates  and  I  equal  lap.  Then 

the  number  of  slates  to  the  square  will  equal  14,400  =  bd~~bl  ^ 


—r-j-    This  formula  may  be  used  for  computing  the  number  of 


120 


BUILDING  STONES  AND  CLAYS 


slates  to  the  square  for  any  given  size  and  lap;  but  for  convenience 
table  64  is  inserted,  which  gives  this  information  for  the  ordinary 
sizes  of  slates  with  a  three-inch  lap. 

TABLE  64.  —  NUMBER  OF  SLATES  PER  SQUARE. 


Size  of  slate. 

Number  of 
slates  per 
square. 

Size  of  slate. 

Number  of 
slates  per 
square. 

Size  of  slate. 

Number  of 
slates  per 
square. 

7X3 

2400 

10X    7 

588 

16X10 

222 

7X4 

1800 

10X  8 

515 

16X12 

185 

7X5 

1440 

12X  6 

534 

18X  9 

214 

8X4 

1440 

12X  7 

458 

18X10 

192 

8X5 

1152 

12X  8 

400 

18X11 

175 

8X6 

960 

12X  9 

356 

18X12 

160 

9X4 

1200 

12X10 

320 

20X10 

170 

9X3 

960 

14X  7 

374 

20X11 

154 

9X6 

800. 

14X  8 

328 

20X12 

142 

9X7 

686 

14X  9 

291 

22X11 

138 

9X8 

600 

14X10 

262 

22X12 

127 

10X4 

1039 

14X12 

219 

24X12 

115 

10X5 

822 

16X  8 

277 

24X14 

98 

10X6 

685 

16  X  9 

247 

The  mille,  which  is  a  unit  much  used  in  Europe,  is  nominally 
1200  slates  of  any  given  size.  As  slates  are  shipped  at  the  pur- 
chaser 's  risk,  however,  60  slates  are  added  to  cover  breakage, 
so  that  the  actual  mille  contains  1260  slates.  The  number  of 
squares  in  a  mille  will  of  course  vary  according  to  the  size  of  the 
slate. 

In  the  English  and  Welsh  slate  trades  certain  fanciful  names 
have  long  been  used  for  the  different  sizes  of  roofing  slates.  These 
names  are  not  always  uniformly  applied  in  the  different  British 
slate  districts,  and  of  late  years  they  seem  to  be  falling  some- 
what into  disuse.  But  as  they  are  still  frequently  met  with  both 
in  export  business  and  in  trade  literature  the  following  table*  has 
been  inserted  in  explanation  of  the  terms. 

*  Notes  on  Building  Construction,  Part  III,  p.  29. 


SLATES 


121 


NAMES  AND  SIZES  OF  BRITISH  SLATES. 


Sold  by  weight. 

Size. 

Sold  by  aize. 

Size. 

Queens  .  .  . 

Inches. 
36X24 

Ladies,  large.  .  .  . 

Inches. 

16  X  8 

Rags.  . 

36X24 

Ladies,  small  

14X12 

Imperials. 

30X24 

Ladies,  small  

14X10 

Sold  by  size. 

Empresses     

26X15 

Ladies,  small  
Ladies,  small  
Doubles  

14X  8 
14X  7 
13X10 

Princesses  

24x14 

Doubles  

13X  7 

Duchesses 

24x12 

Singles 

12X  8 

Marchionesses 

22X12 

Singles 

12  X  6 

Marchionesses  small 

22X11 

Singles 

llX  6 

Countesses 

20X10 

Singles 

10  X  8 

Viscountesses 

18X10 

Singles 

10  X  6 

Viscountesses  small 

18  X  9 

Singles 

10X  5 

Ladies,  large 

16X10 

Thickness.  —  The  thickness  of  a  roofing  slate  varies  usually 
with  the  size  of  the  slate,  decreasing  with  its  area.  In  Welsh 
practice*  the  following  rule  is  observed: 


Size  of  slate. 

Thickness. 

First  quality. 

Second  quality. 

Inches. 
22X11  to  24X12 
16X  8  to  20X10 
13X  7  to  14X12 

Inch. 

! 

Inch. 

Slates  are  graded  according  to  their  smoothness  of  surface, 
even  thickness,  and  (in  some  districts)  uniformity  of  color. 
Usually  two  grades  will  cover  the  output  of  any  given  quarry, 
but  occasionally  a  third  grade  is  employed. 

Roofing  slates  are  always  cut  so  that  the  longer  sides  of  the 
slate  are  in  the  direction  of  the  grain.  This  is  done  not  only  to 
secure  ease  of  dressing,  but  to  give  additional  security  for  slate 
roofs.  If  a  slate  so  cut  be  broken  while  on  the  roof,  the  fracture 
will  be  in  the  direction  of  the  grain,  and  the  two  fragments  of  the 
slate  will  still  be  held  by  single  nails;  while  if  the  slate  had  been  cut 
in  the  opposite  direction  (i.e.,  longer  sides  across  the  grain)  the 
lower  part  of  a  broken  slate  would  have  nothing  to  hold  it  on  the 
roof. 

*  Notes  on  Building  Construction,  Part  III,  p.  28. 


122 


BUILDING  STONES  AND  CLAYS 


Statistics  of  Slate  Production. —  The  following  statistical  tables 
are  quoted  from  the  current  volume  of  Mineral  Resources  United 
States. 

The  following  table  shows  the  total  value  of  the  slate  produced 
in  the  United  States  from  1905  to  1909,  inclusive: 

TABLE  65.  — VALUE   OF   SLATE    PRODUCED   IN   THE   UNITED 
STATES,    1905-1909,   BY  STATES. 


State. 

1905 

1906. 

1907. 

1908. 

1909. 

Arkansas     

$10,000 

$5,000 

$8,500 

$2,500 

California  

40,000 

80,000 

60,000 

60,000 

* 

Georgia 

7500 

5,000 

* 

IVlaine 

224,254 

238,681 

236,606 

213,707 

$227,882 

Maryland 

151,215 

130,969 

116,060 

102,186 

129,538 

New  Jersey          

5,360 

8,000 

j       * 

New  York  
Pennsylvania  
Vermont  
Virginia 

66,646 
3,491,905 
1,352,541 
146,786 

72,360 
3,522,149 
1,441,330 
172,857 

83,485 
3,855,640 
1,477,259 
173,670 

>    130,619 

3,902,958 
1,710,491 
194,356 

I     107,436 

2,892,358 
1,841,589 
180,775 

Other  States  t 

61,840 

Total 

5,496,207 

5,668,346 

6,019,220 

6,316,817 

5,441,418 

Included  in  "  Other  States." 


t  Includes  California,  Georgia  and  New  Jersey. 


The  following  table  shows  the  value  of  slate  produced  for 
roofing  and  for  mill  stock  from  1905  to  1909,  inclusive: 

TABLE  66.  —  VALUE  OF  ROOFING  SLATE  AND  MILL 
STOCK,  1905-1909. 


Roofing  slate. 

Value  of  mill  stock. 

Total  value. 

Number  of  squares. 

Value. 

1905 
1906 
1907 
1908 
1909 

1,241,227 
1,214,742 
1,277,554 
1,333,171 
1,133,713 

$4,574,550 
4,448,786 
4,817,769 
5,186,167 
4,394,597 

$921,657 
1,219,560 
1,201,451 
1,130,650 
1,046,821 

$5,496,207 
5,668,346 
6,019,220 
6,316,817 
5,441,418 

The  following  table  shows  the  average  price  of  roofing  slate 
per  square  in  the  entire  United  States  since  1902: 


1902. 
1903. 
1904. 
1905. 


$3.45 
3.88 
3.78 
3.69 


1906. 
1907. 
1908. 
1909. 


$3.66 
3.77 
3.89 
3.87 


SLATES 


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BUILDING  STONES  AND   CLAYS 


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SLATES  125 


EXPORTS. 

In  comparison  with  the  total  output,  the  value  of  roofing 
slate  exported  from  this  country  in  1909  was  very  small,  being 
$209,383;  in  1908,  $197,216  was  the  value  of  slate  exported. 


IMPORTS. 

Practically  no  slate  is  imported  into  the  United  States.  In 
1908  slate  valued  at  $7227  was  imported  in  the  form  of  mantels, 
chimney  pieces,  roofing  slate,  slabs,  etc.;  in  1909,  the  importa- 
tions were  valued  at  $7872,  and  included  the  same  articles. 

List  of  References  on  Slate  Deposits.  —  In  the  reference  list 
following,  only  such  American  reports  are  listed  as  have  appeared 
after  the  publication  of  Dale's  general  report  on  the  slate  de- 
posits of  the  United  States. 

United  States: 

Dale,  T.  N.,  and  others.  Slate  deposits  and  slate  industry  of  the  United 
States.  Bull.  275,  U.  S.  Geol.  Sur.,  154  pages.  1906. 

Dale,  T.  N.  Note  on  a  black  roofing  slate  from  Nevada.  Mineral  Re- 
sources U.  S.  for  1908,  Vol.  2,  p.  532.  1909. 

Lewis,  J.  V.  Building  stones  of  New  Jersey.  Ann.  Rep.  State  Geol. 
N.  J.  for  1908.  pp.  99-107  devoted  to  New  Jersey  slates. 

Perdue,  A.  H.  The  slates  of  Arkansas.  Bull.  430,  U.  S.  Geol.  Sur.,  pp. 
317-334.  1910. 

Great  Britain: 

Davies,  D.  C.     A  treatise  on  slate  and  slate  quarrying.     12mo.,  pp.  186, 

4th  ed.     London,  1899. 
Hull.     The  building  and  ornamental  stones  of  Great  Britain,  etc..  8vo., 

London.  1782.     British  slates  discussed  on  pp.  286-298. 
Kinahan,  G.  H.     The  redevelopment  of  the  slate  trade  in  Ireland.    Trans. 

Inst.  (Brit.)  Min.  Engrs.,  Vol.  25,  pp.  670-677.     1903. 
Marr,  J.  E.     Notes  on  the  geology  of  the  English  lake  district.     Proc. 

Geol.  Assoc.,  Vol.  16,  pp.  449-483.     1900. 
Postlethwaite,   J.     The   geology  of  the  English  lake  district.     Trans. 

Inst.  (Brit.)  Min.  Engrs.,  Vol.  25,  pp.  302-330.     1903. 
Reade,  T.  M.,  and  Holland,  P.     The  green  slates  of  the  Lake  district. 

Quarry,  Jan.  1,  1902. 
Thomas,    J.    J.     Westmoreland   slates;   their   geology,   chemistry,   and 

architectural    value.     Jour.    Royal    Inst.    Brit.    Arch.,    3d    series, 

Vol.  3,  pp.  194-200.     1896. 
Anon.     The  Welsh  slate  quarries.     Eng.  and  Min.  Jour.,  Dec.  31,  1898. 


126  BUILDING  STONES  AND  CLAYS 

Continental  Europe: 

Bennett,  H.  D.    The  slate  quarries  of  Angers  (France),  U.  S.  Cons.  Rep., 

No.  124,  p.  115,  Jan.,  1891. 

H.  J.  W.    Thuringian  quarries.     Stone,  September,  1896. 
Kruger,   R.     Die  naturlichen  Gesteine.     Leipzig,   1889.    pp.   123-136, 

slates. 

Watrin,  N.     Les  ardoisieres  des  Ardennes.     Charleville,  1898. 
Anon.    Stones  from  Norway  and  Sweden.     Stone,  April,  1896. 


CHAPTER  VIII. 
SANDSTONES. 

Scope  of  Term  Sandstone.  —  The  term  sandstone  is  here  used 
in  a  general  way  to  include  all  the  sedimentary  rocks  which  have 
originated  through  the  consolidation  of  beds  of  sand  or  gravel,  as 
well  as  the  scarcer  beds  of  tuff.  In  this  sense  the  sandstones  are 
purely  mechanical  deposits,  always  of  immediate  sedimentary 
origin,  and  are  predominantly  siliceous  in  composition.  As  noted 
in  a  later  paragraph,  the  term  sandstone  as  here  used  covers  not 
only  the  sandstones  proper,  but  also  the  conglomerates  and  breccias. 

ORIGIN  AND   COMPOSITION. 

Origin  of  Sandstones.  —  The  sandstones  have  originated 
through  the  gradual  consolidation  of  beds  of  sand  and  gravel, 
this  consolidation  being  primarily  due  to  the  pressure  of  over- 
lying beds  exerted  during  long  periods  of  time.  Such  pressure, 
acting  alone,  would  probably  have  been  insufficient  to  secure 
any  high  degree  of  consolidation.  In  most  cases,  however,  a 
cementing  material  of  some  sort  was  either  originally  present  in 
the  beds  of  sand,  or  was  introduced  at  some  later  period,  so 
that  the  present  degree  of  consolidation  is  due  to  the  combined 
effects  of  pressure  and  cementing  material.  In  some  cases,  the 
cementing  material  was  clay  originally  deposited  with  the  sand; 
but  in  the  majority  of  instances  the  cementation  was  effected  by 
the  infiltration  of  waters  containing  dissolved  silica,  lime  car- 
bonate, or  iron  oxide.  Whether  these  mineral-bearing  waters 
permeated  the  sand  bed  before  it  was  covered  by  other  deposits, 
or  whether  they  were  subsequently  introduced  into  the  rock,  the 
final  effect  was  the  same,  for  the  dissolved  substances  were 
ultimately  precipitated  around  and  between  the  grains  of  sand, 
so  as  to  cement  them  together. 

The  result  of  this  method  of  origin  is  that,  on  examining  any 
sandstone  or  conglomerate,  two  different  types  of  constituents 

127 


128 


BUILDING  STONES  AND  CLAYS 


can  usually  be  determined.  First,  there  are  a  multitude  of 
grains  or  pebbles  of  sand,  gravel,  etc.  Second,  surrounding  and 
cementing  these  grains  together  is  a  matrix  of  clay,  of  clear  silica, 
of  iron  oxide,  or  of  lime  carbonate,  as  the  case  may  be. 

Origin  of  Tuffs.  —  Owing  to  their  considerable  extent  and  im- 
portance in  the  western  United  States,  one  particular  class  of 
sandstones  deserves  separate  mention  here,  since  both  in  origin 
and  in  composition  it  differs  from  the  normal  type  of  sandstone. 
The  class  in  question  is  that  which  includes  the  tuffs,  which  are 
beds  of  consolidated  volcanic  ash.  When  volcanic  ash  falls  upon 
a  land  area,  it  rarely  becomes  sufficiently  consolidated  to  be  of 
structural  importance.  If  it  falls  into  lake  basins  or  other  bodies 
of  water,  or  if  it  is  carried  by  running  water  into  such  basins 
without  being  mixed  with  much  other  material,  the  water- 
deposited  beds  of  ash  may  later  become  almost  as  hard  as  other 
sandstones. 

Chemical  Composition  of  Sandstones.  —  The  sandstones  vary 
considerably  in  chemical  composition,  the  variation  being  due 
not  only  t»  differences  in  the  character  of  the  original  grains, 
but  to  differences  in  the  composition  of  the  cementing  material. 


TABLE  69.  —  AVERAGE  ANALYSES  OF  AMERICAN 
SANDSTONES. 


A. 

B. 

Silica  (SiO2) 

78.66 

84.86 

Alumina  (A12O3)  * 

5.03 

6.37 

Ferric  oxide  (Fe2Os).                               .       

1.08 

1.39 

Ferrous  oxide  (FeO)                       

0.30 

0.84 

Lime  (CaO)                        

5.52 

1.05 

IMasrnesia  (JVIffO) 

1.17 

0.52 

Soda  (Na2O) 

0.45 

0.76 

Potash  (K2O)       '                                          

1.32 

1.16 

Phosphorus  pentoxide  (P2Os)    

0.08 

0.06 

Sulphur  trioxide  (SOs) 

0  07 

0.09 

Carbon  dioxide  (CO2) 

5.04 

1.01 

(Combined  water  f                                            

1.33 

1.47 

JVtoisture                                                     

0.31 

0.27 

Including  titanic  oxide  (TiO2). 


t  Including  organic  matter. 


A.  Composite  analysis  of  253  samples  of  American  sandstones,  use  not 

stated.     H.  N.  Stokes,  analyst. 

B.  Composite  analysis  of  371  samples  of  American  sandstones  used  for 

,  building  purposes.     H.  N.  Stokes,  analyst. 


SANDSTONES  129 

A  sandstone  composed  of  quartz  grains,  cemented  by  quartz, 
would  naturally  show  on  analysis  a  very  high  silica  percentage. 
On  the  other  hand,  a  sandstone  composed  of  grains  of  quartz, 
feldspar,  mica,  etc.,  cemented  together  by  iron  oxide  or  lime  car- 
bonate, might  not  show  over  75  or  80  per  cent  of  silica. 

It  is  difficult,  from  a  series  of  analyses  such  as  is  given  later,  to 
secure  any  very  definite  idea  of  the  average  composition  of  the 
group  as  a  whole.  This  is  accomplished,  however,  by  Table  69, 
immediately  preceding,  which  gives  average  results  of  consider- 
able interest. 

Value  of  Chemical  Work  on  Sandstones.  —  The  value,  from 
the  engineer's  point  of  view,  of  a  chemical  analysis  of  any  par- 
ticular sandstone  which  may  be  under  investigation  at  the 
moment,  will  depend  upon  a  number  of  factors. 

The  writer's  opinion  on  this  subject  may  be  summarized  as 
follows : 

(a)  If  a  specimen  of  the  stone  is  available  for  examination, 
with  or  without  the  use  of  a  hand  lens,  the  results  reported  by 
the  analyst  can  usually  be  interpreted  with  considerable  confi- 
dence and  accuracy.  In  this  case,  the  chemical  analysis  can  be 
made  to  afford  information  of  distinct  value  to  the  engineer,  for 
ocular  examination  of  the  stone  will  usually  decide  which  of  the 
elements  reported  exists  in  the  component  grains,  and  which  in 
the  cementing  material. 

(6)  If  no  specimen  of  the  stone  is  available,  and  it  happens 
that  some  sort  of  judgment  must  be  given  on  the  basis  of  the 
chemical  analysis  alone,  the  case  is  far  less  satisfactory,  but  still 
not  entirely  hopeless.  Under  these  circumstances,  the  engineer 
must  look  with  suspicion  on  any  lime,  magnesia,  alkalies,  or 
carbon  dioxide  found  in  the  report  of  the  analysis;  and  must 
remember  that,  other  things  being  equal,  the  percentage  of  silica, 
or  at  times  of  silica  plus  alumina  and  iron,  is  a  rough  but  fairly 
trustworthy  index  to  the  structural  value  and  probable  durability 
of  the  stone. 

The  Interpretation  of  the  Chemical  Analysis.  —  A  complete 
analysis  of  a  sandstone,  or,  to  be  more  accurate,  an  analysis 
complete  enough  for  all  practical  purposes,  will  result  in  deter- 
minations of  the  following  constituents:  Silica  (Si02),  alumina 
(A12O3),  ferrous  oxide  (FeO),  ferric  oxide  (Fe203),  lime  (CaO), 
magnesia  (MgO),  potash  (K20),  soda  (Na«0),  carbon  dioxide 


130  BUILDING  STONES  AND  CLAYS 

(CO2),  combined  water,  and  moisture.  In  some  cases  it  may  be 
advisable  to  determine  also  sulphur  and  carbon  or  organic  matter. 

If  the  analysis  be  made  by  an  ordinary  commercial  chemist  it 
may  be  safely  assumed  that  his  results  on  potash  and  soda  are 
absolutely  worthless,  and  that  his  silica  and  alumina  were  not 
completely  separated.  Fortunately,  however,  as  will  be  seen 
later,  these  errors  of  poor  analysts  are  not  so  harmful  as  they 
might  appear,  owing  to  the  curious  fact  that  if  a  deleterious  con- 
stituent be  reported  too  low,  some  other  deleterious  constituent 
will  be  reported  too  high;  while  the  beneficial  constituents  of  the 
sandstone  tend  to  balance  themselves  in  similar  manner. 

As  a  rule  it  will  be  safe  to  assume,  in  trying  to  interpret  a 
sandstone  analysis,  that  the  bulk  of  the  silica  reported  is  repre- 
sented by  the  sand  grains;  and  that  the  other  constituents  re- 
ported —  iron,  lime,  magnesia,  etc.  —  are  probably i  from  the 
cementing  material.  In  any  given  case,  examination  of  a  hand 
specimen  of  the  rock  will  give  a  sufficiently  accurate  idea  of  the 
truth  of  these  assumptions. 

Under  ordinary  conditions,  therefore,  high  percentages  of  lime, 
magnesia,  and  alkalies  are  characteristic  of  the  less  durable 
sandstones;  while  high  silica  is  characteristic  of  the  better  class 
of  stones.  The  type  exemplified  by  the  bluestone  of  New  York 
and  Pennsylvania  must,  however,  be  borne  in  mind,  for  in  this 
type  the  silica  is  not  high,  while  alumina  is  present  in  notable 
quantity,  the  cementing  material  being  clayey  in  composition. 


SANDSTONES 


131 


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SANDSTONES  137 


TEXTURE  AND   PHYSICAL  PROPERTIES. 

Shape  and  Size  of  Grain.  —  The  sedimentary  siliceous  rocks 
are  given  various  names  according  to  their  texture.  If  the  com- 
ponent grains  are  small  and  of  fairly  uniform  size,  the  rock  is 
properly  a  sandstone ;  if  the  rock  contains  numerous  rounded  peb- 
bles, it  is  a  conglomerate  ;  while  if  it  is  composed  of  large  angular 
fragments,  it  is  a  breccia.  Regarded  as  structural  materials,  how- 
ever, the  sandstones  proper  demand  most  consideration,  for 
conglomerates  are  rarely  used  for  building  purposes  while  breccias 
are  still  more  rarely  employed. 

Composition  of  the  Cementing  Material.  —  The  cementing 
material,  as  noted  on  a  preceding  page,  may  be  quartz,  clayey 
matter,  iron  oxide,  or  lime  carbonate;  and  a  descriptive  adjective 
is  frequently  employed  to  describe  these  differences.  When 
quartz  or  silica  is  the  cement,  the  rock  is  a  siliceous  sandstone; 
while  when  iron  oxide  or  lime  carbonate  bond  the  grains  together 
the  terms  "  ferruginous  sandstone  "  and  "  calcareous  sandstone  " 
are  respectively  used.  In  some  sandstones  the  cementing  ma- 
terial is  clayey  or  argillaceous. 

As  regards  the  respective  strength  and  durability  of  sandstones 
with  different  kinds  of  cementing  material,  other  factors  may 
vary  so  much  that  it  is  not  safe  to  rely  on  any  general  rule. 
Other  things  being  equal,  however,  the  best  cementing  material 
is  silica,  followed  by  clay,  iron  oxide,  and  lime  carbonate  in  the 
order  named.  The  last  is  by  far  the  worst. 

Value  of  Microscopic  Work  on  Sandstones.  —  When  a  thin 
section  of  sandstone  is  examined  under  the  petrographic  micro- 
scope, the  investigator  may  hope  to  secure  data  covering  the 
following  points:  (1)  mineral  character  of  the  component  grains; 
(2)  size  and  shape  of  grains;  (3)  mineral  character  of  cementing 
material;  (4)  relative  proportion  of  cementing  material  to  grains. 
In  addition  to  these  four  points,  all  of  which  are  usually  readily 
determinable,  it  is  sometimes  possible  to  form  some  idea  as  to 
(5),  the  probable  tenacity  and  durability  of  the  cementing  ma- 
terial. This  fifth  point  is  the  one  of  greatest  interest  to  the 
engineer,  and  if  it  were  possible  to  express  microscopic  results  on 
this  point  in  some  quantitative  manner  the  trouble  and  expense 
of  the  investigation  would  be  entirely  justified.  Even  as  it  is, 
it  will  be  safest  to  have  the  matter  investigated  in  this  way.  For 


138  BUILDING  STONES  AND   CLAYS 

it  must  always  be  borne  in  mind,  that  in  dealing  with  ordinary 
sandstones  we  are  dealing  with  the  weakest  and  most  uncertain 
of  all  building  stones,  and  that  nothing  should  be  overlooked 
which  may  throw  light  on  the  possible  future  behavior  and 
durability  of  the  particular  sandstone  which  may  be  under 
examination. 

Physical  Properties  of  Sandstones.  —  In  the  following  tables 
are  presented  the  results  of  tests  of  strength,  density,  etc.,  on  a 
large  number  of  American  and  British  sandstones. 


SANDSTONES 


139 


140 


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142 


BUILDING  STONES  AND  CLAYS 


TABLE  72.  —  PHYSICAL  PROPERTIES  OF  SANDSTONES: 
ENGLAND.     (BEARE.) 


Locality. 

Specific 
gravity. 

Pounds  per 
cubic  foot. 

Absorption, 
per  cent. 

Compressive 
strength, 
Ibs.  per  sq. 
inch. 

Prudham  

2.28 

142.5 

4  66 

7080 

Corncockle  

2.125 

132.6 

4.57 

5,970 

Gunnerton 

2  095 

130  8 

5  16 

5  515 

Cragg 

2  18 

136.1 

4  13 

8  925 

Corsehill 

2  09 

130.4 

7  94 

6920 

Polmaise  ...         .       .    . 

2.27 

141.7 

4  58 

8,580 

White  Plean  

2.215 

138.2 

4  25 

9,535 

Arbroath  

2.42 

151.0 

2.32 

8,680 

Auchinlee 

2  065 

128  9 

6  90 

3  170 

Craigleith 

2  22 

138.6 

3  61 

13  410 

White  Hailes                               .    .    . 

2  305 

143.8 

3  71 

10,300 

Dean  Forest  
Gatelawbridge  

2.425 
2.075 

151.4 
129.5 

2.71 

5.84 

8,245 
7,710 

Blue  Hailes 

2  295 

143  2 

4  70 

7  150 

Binnie 

2  165 

135  1 

5  22 

8850 

Hermand 

2.285 

142.6 

4  70 

7,120 

Howley  Park  

2.247 

140.3 

4  90 

7,260 

White  Grinshill  

1.963 

122.5 

7.80 

3,260 

Darley  Top 

2  227 

139  0 

3  40 

8040 

Hercules  Ridge 

2  21 

138  0 

3  60 

5225 

Bramley  Fall             

2.117 

132.2 

3  70 

3,710 

Ackworth     

2.253 

140.7 

5.00 

6,055 

Robin  Hood  

2.313 

144.6 

3.90 

8,930 

Lightcliffe 

2  398 

149  6 

2  30 

15  870 

Aspatria 

1  973 

123  2 

8  50 

3  540 

WORKING  CLASSIFICATION  OF  SANDSTONES. 

The  Necessity  for  Subdivision.  —  It  has  previously  been  stated 
that  sandstones  vary  greatly  in  their  composition,  structure,  and 
other  physical  properties,  and  in  preceding  statements  some 
attention  has  been  paid  to  the  character  and  extent  of  these 
variations.  In  view  of  the  facts  there  developed,  it  will  be 
readily  understood  that  it  is  very  difficult  to  frame  a  subclassifi- 
cation  of  sandstones  which  shall  be  detailed  enough  to  include 
all  the  important  types  and  which  shall  at  the  same  time  be 
serviceable  for  general  use.  On  the  other  hand,! (it  is  absolutely 
necessary,  from  the  engineering  point  of  view,  that  some  such 
grouping  be  formulated,  for  without  some  attempt  at  subdivision 
it  would  be  impossible  to  discuss  satisfactorily  the  physical  and 
industrial  properties  of  a  class  including  such  diverse  members. 

Class  A.  Quartzites  and  Quartzitic  Sandstones.  —  Dense, 
1  compact  stones,  composed  of  sand  grains  imbedded  in  a  siliceous 


SANDSTONES  143 

ground  mass;  occasionally  the  cementing  material  also  contains 
iron  oxide,  but  never  lime  or  clay,  and  the  silica  is  always  pre- 
dominant. Owing  to  their  composition  and  structure,  their 
porosity  and  absorption  are  always  low,  and  their  compressive 
strength  high.  Prominent  American  examples  of  this  group  are 
the  Kettle  River  sandstone  of  Minnesota,  and  the  Ablemans 
quartzite  of  Wisconsin.  Both  in  this  country,  in  Canada,  and 
in  Europe  stones  of  this  class  occur  almost  exclusively  in  the 
pre-Cambrian  and  Cambrian  geologic  periods. 

Class  B.  Graywackes  and  Dense  Flagstones.  —  The  stones 
of  this  group  are  often  as  dense  and  compact  as  those  of  Class  A. 
Like  them  the  constituent  grains  are  commonly  of  pure  silica 
(sand),  but  the  cementing  material  usually  contains  not  only 
silica  but  also  clay,  and  occasionally  notable  percentages  of  iron 
oxide;  never,  however,  does  it  contain  more  than  a  trace  of  lime 
carbonate.  In  this  class  the  density  is  not  due  so  much  to  the 
thorough  cementation  by  silica,  as  to  the  effects  of  long-continued 
pressure  acting  on  a  more  clayey  cementing  material.  Stones 
of  this  group  include  most  of  the  "  graywackes  "  of  Europe,  the 
well-known  Hudson  River  bluestone  of  New  York,  and  other 
prominent  flagging  stones.  Since  long  pressure  and  at  least  mild 
heat  were  necessary  for  their  consolidation,  stones  of  Class  B 
are  commonly  found  in  the  Cambrian,  Silurian,  and  Devonian 
rocks,  and  rarely  higher  (at  least  in  the  greater  portion  of  the 
United  States). 

Class  C.  Normal  Sandstones,  Including  most  "  Freestones." 
-  In  this  class  would  be  included  the  sandstones  of  medium  den- 
sity and  strength  which  comprise  the  bulk  of  the  sandstones  used 
for  ordinary  building  operations.  They  are  markedly  lower  in 
density  and  hardness  than  the  stones  of  Classes  A  and  B.  Owing 
partly  to  this  fact,  they  are  more  readily  cut  and  dressed  in  all 
directions  than  are  the  more  resistant  quartzites  and  flagstones. 

Class  D.    Porous  Sandstones.  —  This  class  includes  a  number  ,J 
of  porous,  loosely  compacted  sandstones,  much  inferior  for  all 
structural  purposes  to  those  included  in  the  preceding  classes. 
Many  of  them,  the  Acquia  Creek  sandstone  of  Virginia  being  a 
well-known  example,  are  of  relatively  recent  geologic  age. 

Geologic  Distribution  of  Sandstones.  —  Since  sand  beds  have 
formed  in  all  ages  from  the  pre-Cambrian  to  the  present  day,  it 
is  no  matter  for  surprise  that  commercial  sandstones  are  found 


144 


BUILDING  STONES  AND  CLAYS 


representing  almost  all  of  the  different  geologic  periods.  In  this 
respect  sandstones  show  a  far  wider  and  more  general  distribu- 
tion than  the  granites,  and  probably  wider  even  than  the  lime- 
stones. 

The  three  most  important  quarry  areas  of  the  United  States 
operate  respectively  on: 

1.  The  Devonian  "  bluestones  "  of  New  York  and  Pennsyl- 
vania. 

2.  The  Devonian  and  Carboniferous  sandstones  of  Ohio. 

3.  The  Triassic  "  brownstones  "  of  the  middle  Atlantic  states, 
Massachusetts,  and  Connecticut. 

Production  of  Sandstone  in  the  United  States.  —  The  tables 
following,  revised  from  those  annually  published  by  the  United 
States  Geological  Survey,  contain  data  on  the  American  sand- 
stone industry,  covering  a  series  of  years. 

TABLE  73.  —  SANDSTONE  PRODUCTION  OF  THE  UNITED 
STATES,  1899-1909. 


Year. 

Value. 

Year. 

Value. 

1899 

$5,725,395 

1905 

$10,006,774 

1900 

6,471,384 

1906 

9,169,337 

1901 

8,138,680 

1907 

8,871,678 

1902 

10,594,483 

1908 

7,594,091 

1903 

11,262,259 

1909 

8,010,454 

1904 

10,273,891 

1910 

7,930,019 

SANDSTONES 


145 


TABLE  74.  —  SANDSTONE  PRODUCTION  OF  THE  UNITED 
STATES,   1905-1909,  BY  STATES. 


State. 

1905. 

1906. 

1907. 

1908. 

1909. 

Alabama  
Arizona  

$28,107 
65,558 
58,161 
685,668 
453,029 
62,618 
22,265 
29,115 
15,421 
9,335 
79,617 
280,579 
12,984 
367,461 
123,123 
294,640 
27,686 
45,116 
120 
1,500 
294,719 
101,522 
*  1,831,756 
4,483 
1,055 
1,744,472 
15,112 
1,229 
h  2,487,939 
193,408 
8,715 
123,281 
43,429 
2,000 
124,910 
171,309 
161,741 
33,591 

$40,467 
33,149 
55,703 
642,166 
286,544 

(a) 

11,969 
19,125 
30,740 
5,600 
42,809 
125,123 
9,533 
260,721 
65,395 
285,433 
20,951 
37,462 
6,899 

$48,673 
158,435 
94,275 
437,738 
299,443 

(a) 

24,001 
14,996 
15,425 
3,542 
46,831 
98,450 
13,859 
243,323 
53,003 
300,204 
35,289 
39,216 
11,609 

$34,099 
396,358 
42,463 
330,214 
181,051 
55,949 
33,394 
12,218 
3,342 
2,337 
67,950 
78,732 
6,262 
241,462 
39,103 
197,184 
17,954 
51,564 
d  15,815 

(e) 
154,422 
a  10,410 
*  1,774,843 
»  12,266 

« 

1,244,752 
57,124 

w 

*  1,368,784 
128,554 

(m) 

154,948 
25,097 

(m) 

464,587 
127,149 
219,130 
44,574 

$77,327 
298,335 
67,956 
290,034 
197,105 

(*) 
29,263 
26,891 
4,119 
2,443 
19,560 
90,835 
10,584 
'  457,962 
36,084 
299,358 
28,763 
73,443 
.  _  .  . 

189,098 
4,963 
*  1,430,830 

Arkansas  

California  
Colorado  
Connecticut  
Idaho 

Illinois  

Indiana  

Iowa  

Kansas  

Kentucky  
Maryland 

Massachusetts  
Michigan  
Minnesota  

Missouri  

Montana 

Nebraska 

Nevada 

New  Jersey  
New  Mexico  
New  York  
North  Carolina.  .  .  . 
North  Dakota  
Ohio 

215,142 
42,574 
^1,905,892 
3,531 
44 
1,426,645 
40,861 
25,950 
h  2,724,874 
145,966 
14,136 
111,533 
137,529 
5,100 
169,500 
113,369 
181,986 
24,715 

177,667 
12,450 
Acl,978,117 
4,105 
3,260 
1,591,148 
43,403 
3,904 
^  2,064,913 
143,585 
16,523 
108,047 
24,298 

(n) 

295,585 
o  197,926 
236,183 
32,252 

(V) 

1,639,006 
59,855 
04,811 
*  1,637,  794 
*  118,029 

(n) 

61,600 
71,235 
28,574 
335,470 
P  201,  038 
204,959 
13,130 

Oklahoma  
Oregon 

Pennsylvania   .  . 

South  Dakota.  .  .  . 

Tennessee  

Texas  

Utah  

Virginia 

Washington  
West  Virginia 

Wisconsin 

Wyoming  

Total  

10,006,774 

9,169,337 

8,871,678 

7,594,091 

8,010,454 

a  Included  in  New  York. 

6  Included  in  Massachusetts. 

c  Includes  Connecticut. 

d  Includes  North  Dakota  and  Oregon. 

e  Included  with  New  Mexico. 

/  Included  in  Oregon. 

g  Includes  Nevada. 

h  Includes  bluestone. 


i  Includes  Tennessee  and  Virginia. 
j  Included  with  Nebraska. 
k  Included  in  South  Dakota. 
I  Includes  North  Dakota. 
m  Included  with  North  Carolina, 
n  Included  in  West  Virginia. 
o  Includes  a  small  value  for  Virginia, 
p  Includes  Tennessee. 


146 


BUILDING  STONES  AND  CLAYS 


TABLE  75.  —  SANDSTONE  PRODUCTION,  1903-1909,   BY  USES. 


Year. 

Building  stone. 

Rubble  and 
riprap. 

Paving,  curbing, 
and  flags. 

Crushed  stone. 

Canister. 

1903 

$6,403,969 

$917,080 

$2,863,737 

$827,585 

$187,689 

1904 

5,125,858 

799,251 

3,045,917 

1,041,493 

136,957 

1905 

4,702,189 

818,870 

3,008,013 

1,008,270 

186,123 

1906 

4,275,669 

756,762 

2,866,802 

889,894 

284,066 

1907 

3,154,783 

845,859 

3,451,238 

987,528 

308,520 

1908 

2,605,381 

1,039,929 

2,747,489 

906,317 

175,325 

1909 

3,349,519 

642,533 

2,493,250 

1,212,931 

240,409 

TABLE  76.  —  VALUE  AND  USES  OF  BLUESTONE  PRODUCED 
IN  NEW  YORK  AND  PENNSYLVANIA  IN  1908  AND   1909. 


1908. 


State. 

Building 
purposes. 

Flagging. 

Curbing. 

Crushed 
stone. 

Other 
purposes. 

Total  value. 

New  York  
Pennsylvania.  .  . 

Total  

$415,652 
186,093 

$413,920 
217,690 

$313,319 
116,197 

$9,219 
6,985 

$68,852 
14,933 

$1,220,962 
541,898 

601,745 

631,610 

429,516 

16,204 

83,785 

1,762,860 

1909. 


New  York  
Pennsylvania  .  .  . 

Total  

$378,960 
159,193 

«  $264,770 
c  195,525 

b  $241,  253 
<*  83,538 

$21,224 
70,269 

$11,389 
20,281 

$917,596 
528,806 

538,153 

460,295 

324,791 

91,493 

31,670 

1,446,402 

a  This  value  represents  4,129,324  square  feet  of  stone. 
6  This  value  represents  1,968,329  linear  feet  of  stone, 
c  This  value  represents  2,665,480  square  feet  of  stone. 
d  This  value  represents  437,281  linear  feet  of  stone. 


SANDSTONES 


147 


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148  BUILDING  STONES  AND   CLAYS 

List  of  References  on  Sandstones.  —  The  following  list  covers 
the  principal  papers  and  reports  dealing  with  the  sandstones  of 
the  United  States. 

Arkansas: 

Griswold,  L.  S.     Whetstones  and  the  novaculites  of  Arkansas.     Ann. 

Rep.  Ark.  Geol.  Sur.  for  1890,  Vol.  3,  443  pp.     1892. 
California: 

Jackson,  A.  W.     Building  stones  (of  California).     7th  Ann.  Rep.  Cal. 

State  Mineralogist,  pp.  206-217. 
Anon.     Sandstones  of  California.     Bull.  38,  Cal.  State  Min.  Bureau,  pp. 

114-146.     1906. 
Indiana: 

Hopkins,  T.  C.  The  Carboniferous  sandstones  of  western  Indiana. 
20th  Ann.  Rep.  Indiana  Dept.  Geol.,  pp.  188-328.  1896.  Also  re- 
printed partly  in  Stone,  Vol.  13,  pp.  227-238,  334-342,  456-466. 
Abstracts  also  appeared  in  the  Mineral  Industry,  Vol.  4,  pp.  559-564 
and  in  17th  Ann.  Rep.  U.  S.  Geol.  Sur.,  pt.  3,  pp.  780-787. 
Kindle,  E.  M.  The  whetstone  and  grindstone  rocks  of  Indiana.  20th 

Ann.  Rep.  Indiana  Dept.  Geol.,  pp.  329-368.     1896. 
Iowa: 

Bain,  H.  F.     Properties  and  tests  of  Iowa  building  stones.     Rep.  Iowa 

Geol.  Sur.,  Vol.  8,  pp.  370-416.     1898. 
Kansas: 

Bailey,  E.  H.  S.,  and  Case,  E.  C.     On  the  composition  of  some  Kansas 

building  stones.     Trans.  Kan.  Acad.  Sci.,  Vol.  13,  p.  78. 
Minnesota: 

Winchell,  H.  V.     Minnesota  Sandstones.     Stone,  Dec.,  1896. 

.     Minnesota  quartzites.     Stone,  Vol.    14,   pp.    122-125. 

1897. 


Crider,  A.  F.     The  geology  and  mineral  resources  of  Mississippi.     Bull. 
283,  U.  S.  Geol.  Sur. 

New  Jersey: 

Kiimmel,  H.  B.     The  Newark  system  or  red  sandstone  belt  (of  N.  J.). 

Ann.  Rep.  N.  J.  State  Geol.  for  1898,  pp.  23-159.     1898. 
New  York: 

Bishop,  I.  P.     Structural  and  economic  geology  of  Erie  County.     15th 

Ann.  Rep.  N.  Y.  State  Geol.,  Vol.  1,  pp.  305-392.     1897. 
Dickinson,  H.  T.     Quarries  of  bluestone  and  other  Devonian  sandstones 

of  New  York  State.     Bull.  61,  N.  Y.  State  Museum,  112  pp.     1903. 
Eckel,  E.  C.     The  quarry  industry  in  southeastern  New  York.     20th 

Ann.  Rep.  N.  Y.  State  Geol.,  pp.  141-176.     1902. 

Gordon,  J.  B.     The  bluestone  industry  of  New  York.     Stone,  July,  1899. 
Ingram,  H.  B.     The  great  bluestone  industry.     Popular  Science  Monthly, 

Vol.  45,  pp.  352-359.     1894. 


SANDSTONES  149 

Lincoln,  D.  F.     Report  on  the  structural  and  economic  geology  of  Seneca 

County.     14th  Ann.  Rep.  N.  Y.  State  Geol.,  pp.  60-125.     1895. 
Smock,  J.  C.     Building  stone  in  the  State  of  New  York.     Bull.  3,  N.  Y. 

State  Museum,  152  pp.     1888. 
Smock,  J.  C.     Building  stone  in  New  York.     Bull.   10,  N.  Y.  State 

Museum,  396  pp.     1890. 
Winchell,  N.  H.     The  Potsdam  sandstone  at  Potsdam,  N.  Y.     21st  Ann. 

Rep.  Minn.  Geol.  Sur.,  pp.  99-111.     1893. 
Ohio: 

Orton,  E.     The  Berea  sandstone  of  Ohio.     Rep.  Ohio  Sec.  of  State  for 

1878,  pp.  591-599.     1879. 
Pennsylvania: 

Hopkins,  T.  C.     The  building  materials  of  Pennsylvania:  I,  Brownstones. 
Appendix  to  Ann.  Rep.  Penn.  State  Coll.  for  1896,  122  pp.     1897. 
Reprinted  in  part  in  18th  Ann.  Rep.  U.  S.  Geol.  Sur.,  pt.  5,  pp. 
1025-1043. 
West  Virginia: 

Grimsley,  G.  P.     The  sandstones  of  West  Virginia.     Bull.  4,  W.  Va.,  Geol. 

Sur.,  pp.  355-595.     1909. 
Wisconsin: 

Buckley,  E.  R.     Building  and  ornamental  stones  of  Wisconsin.     Bull.  4, 

Wis.  Geol.  Sur.,  500  pp.     1898. 
Wyoming: 

Knight,  W.  C.     The  building  stones  and  clays  of  Wyoming.    Eng.  and 
Min.  Jour.,  Vol.  66,  pp.  546,  547.     1898. 


CHAPTER  IX. 
LIMESTONES. 

THOUGH  marbles  are,  from  a  strictly  geological  point  of  view, 
merely  special  varieties  of  limestone,  they  occupy  so  distinct  a 
position  in  the  stone  trade  as  to  require  separate  consideration. 
For  this  reason  the  two  classes  of  stone  will  be  treated  in  separate 
chapters  in  the  present  volume ;  Chapter  IX  being  devoted  to  the 
consideration  of  the  ordinary  structural  limestones,  while  Chap- 
ter X  will  contain  data  on  the  marbles  and  decorative  limestones. 
The  origin  of  limestones  in  general  will  of  course  be  discussed  in 
the  present  chapter. 

ORIGIN  AND   CHEMICAL  COMPOSITION. 

Origin  of  Limestones.*  —  Limestones  have  been  formed  largely 
by  the  accumulation  at  the  sea  bottom  of  the  calcareous  remains 
of  such  organisms  as  the  foraminifera,  corals,  and  molluscs. 
Many  of  the  thick  and  extensive  limestone  deposits  of  the  United 
States  were  probably  deep-sea  deposits  formed  in  this  way. 
Some  of  these  limestones  still  show  the  fossils  of  which  they 
were  formed,  but  in  others  all  trace  of  organic  origin  has  been 
destroyed  by  the  fine  grinding  to  which  the  shells  and  corals 
were  subjected  before  their  deposition  at  the  sea  bottom.  It  is 
probable  also  that  part  of  the  calcium  carbonate  of  these  lime- 
stones was  a  purely  chemical  deposit  from  solution,  cementing 
the  shell  fragments  together. 

A  far  less  extensive  class  of  limestones,  though  very  important 
in  the  present  connection,  owe  their  origin  to  the  indirect  action 
of  organisms.  The  "  marls,"  which  have  until  recently  been  so 
important  as  Portland-cement  materials,  fall  in  this  class.  As 
the  class  is  of  limited  extent,  and  includes  no  products  used  in 
structural  work,  its  method  of  origin  may  be  dismissed  here. 

Deposition  from  solution  by  purely  chemical  means  has  un- 

*  For  a  more  detailed  discussion  of  this  subject  the  reader  will  do  well  to 
consult  Chapter  VIII  of  Prof.  J.  F.  Kemp's  "  Handbook  of  Rocks." 

150 


LIMESTONES 


151 


doubtedly  given  rise  to  numerous  important  limestone  deposits. 
When  this  deposition  took  place  in  caverns  or  in  the  open  air  it 
gave  rise  to  onyx  deposits  and  to  the  " travertine  marls"  of  cer- 
tain Ohio  and  other  localities;  when  it  took  place  in  isolated  por- 
tions of  the  sea,  through  the  evaporation  of  the  sea  water,  it  gave 
rise  to  the  limestone  beds  which  so  frequently  accompany  de- 
posits of  salt  and  gypsum. 

Shells  as  Sources  of  Limestone.*  —  Most  molluscan  shells  con- 
sist essentially  of  lime  carbonate,  with  commonly  very  small  per- 
centages (less  than  1  per  cent)  of  magnesium  carbonate,  and 
traces  of  alkalies,  phosphoric  acid,  etc.  The  analyses  given  in 
Table  78  will  serve  to  illustrate  the  composition  of  the  shells  of 
three  common  species  of  molluscs. 

TABLE  78.  —  ANALYSES  OF  VARIOUS  MOLLUSCAN  SHELLS. 


» 

2 

3 

4 

5 

6 

Silica  (SiO2)  

3.30 

1.49 

n.d. 

0.20 

0.16 

n.d. 

Alumina  (AUOi) 

0  08 

Iron  oxide  (Fe2O3) 

0  17 

0  04 

nd. 

0  04 

Lime  (CaO) 

52  14 

53  37 

n.d. 

52  86 

54  55 

54  38 

Magnesia  (MgO) 

0  25 

Alkalies  (K2O,  Na->O) 

0  35 

Sulphur  trioxide  (SO3) 

0  16 

0  81 

0  80 

0  35 

0  28 

0  28 

Phosphorus  pentoxide  (PzO^)  
Carbon  dioxide  (CO2)  
Water  

n.d. 
41.61 

0.11 
40.60 

n.d. 
n.d. 

0.05 
41.02 

0.001 
42.82 

n.d. 
n.d. 

Organic  matter  

2.32 

3.48 

3.17 

5.02 

2  01 

2  04 

1.  Oyster  shell;  L.  P.  Brown  and  J.  S.  H.  Koiner,  analysts;  American 

Chemical  Journal,  Vol.  11,  pp.  36-37. 

2,  3.   Oyster  shell;  How,  analyst;  American  Journal  of  Science,  2d  series, 

Vol.  41,  p.  380. 

4.  Mussel  shell;  How,  analyst;  American  Journal  of  Science,  2d  series, 

Vol.  41,  p.  380. 

5,  6.   Periwinkle  shell;  How,  analyst;  American  Journal  of  Science,  2d 

series,  Vol.  41,  pp.  379-381. 

These  analyses  show  that  in  ordinary  practice  an  oyster  shell 
may  be  expected  to  contain,  as  its  principal  impurities,  several 

*  Brown,  L.  P.,  and  Koiner,  J.  S.  H.  Analysis  of  oyster  shells  and  oyster- 
shell  lime.  American  Chemical  Journal,  Vol.  11,  pp.  36,  37.  1889. 

How,  Dr.  On  the  comparative  composition  of  some  recent  shells,  a  Silurian 
fossil  shell,  and  a  Carboniferous  shell  limestone.  American  Journal  of  Science 
2d  series,  Vol.  41,  pp.  379-384.  1866. 


152  BUILDING  STONES  AND  CLAYS 

per  cent  of  organic  matter  and  from  a  trace  to  5  per  cent  of  silica, 
iron  oxide,  and  alumina.  The  amount  of  these  last  clayey  im- 
purities present  will  doubtless  vary  with  the  cleanness  of  the 
shell,  as  it  is  probable  that  they  are  in  large  part  purely  external 
impurities. 

Chemical  Composition  of  Limestone.  —  Calcite,  a  rock-forming 
mineral  in  all  limestones,  is  carbonate  of  lime.  A  theoretically  pure 
limestone  is  merely  a  massive  form  of  the  mineral  calcite.  Such 
an  ideal  limestone  would  therefore  consist  entirely  of  calcium  car- 
bonate or  carbonate  of  lime,  with  the  formula  CaC03(CaO+C02), 
corresponding  to  the  composition  calcium  oxide  (CaO)  56  per 
cent,  carbon  dioxide  or  carbonic  acid  (CO2)  44  per  cent. 

As  might  be  expected,  the  limestones  we  have  to  deal  with  in 
practice  depart  more  or  less  widely  from  this  theoretical  com- 
position. These  departures  from  ideal  purity  may  take  place 
along  either  of  two  lines: 

a.   The  presence  of  magnesia  in  place  of  part  of  the  lime; 
6.   The  presence  of  silica,  iron,  alumina,  alkalies,  or  other 
impurities. 

It  seems  advisable  to  discriminate  between  these  two  cases, 
even  though  a  given  sample  of  limestone  may  fall  under  both 
heads,  and  they  will  therefore  be  discussed  separately. 

The  Presence  of  Magnesia  in  Place  of  Part  of  the  Lime.  —  The 
theoretically  pure  limestones  are,  as  above  noted,  composed 
entirely  of  calcium  carbonate  and  correspond  to  the  chemical 
formula  CaCO3.  Setting  aside  for  the  moment  the  question  of 
the  presence  or  absence  of  such  impurities  as  iron,  alumina,  silica, 
etc.,  it  may  be  said  that  lime  is  rarely  the  only  base  in  a  lime- 
stone. During  or  after  the  formation  of  the  limestone  a  certain 
percentage  of  magnesia  is  usually  introduced  in  place  of  part  of 
the  lime,  thus  giving  a  more  or  less  magnesian  limestone.  In 
such  magnesian  limestones  part  of  the  calcium  carbonate  is 
replaced  by  magnesium  carbonate  (MgC03),  the  general  formula 
for  a  magnesian  limestone  being,  therefore, 

x  CaCO3  +  y  MgCO3. 

In  this  formula  x  may  vary  from  100  per  cent  to  zero,  while  y 
will  vary  inversely  from  zero  to  100  per  cent.  In  the  particular 
case  of  this  replacement  where  the  two  carbonates  are  united 
in  equal  molecular  proportions,  the  resultant  rock  is  called  dolo- 


LIMESTONES  153 

mite.  It  has  the  formula  CaCO3MgC03,  corresponding  to  the 
composition  calcium  carbonate  54.35  per  cent,  magnesium  car- 
bonate 45.65  per  cent.  In  the  case  where  the  calcium  carbonate 
has  been  entirely  replaced  by  magnesium  carbonate,  the  result- 
ing pure  carbonate  of  magnesia  is  called  magnesite,  having  the 
formula  MgC03  and  the  composition  magnesia  (MgO)  47.6  per 
cent,  carbon  dioxide  (CO2)  52.4  per  cent. 

Rocks  of  this  series  may  therefore  vary  in  composition  from 
pure  calcite  limestone  at  one  end  of  the  series  to  pure  magnesite 
at  the  other.  The  term  limestone  has,  however,  been  restricted 
in  general  use  to  that  part  of  the  series  lying  in  composition  be- 
tween calcite  and  dolomite,  while  all  those  more  uncommon 
phases  carrying  more  magnesium  carbonate  than  the  45.65  per 
cent  of  dolomite  are  usually  described  simply  as  more  or  less 
impure  magnesites. 

Though  magnesia  is  often  described  as  an  "  impurity  "  in 
limestone,  this  word,  as  can  be  seen  from  the  preceding  state- 
ments, hardly  expresses  the  facts  in  the  case.  The  magnesium 
carbonate  present,  whatever  its  amount,  simply  serves  to  replace 
an  equivalent  amount  of  calcium  carbonate,  and  the  resulting 
rock,  whether  little  or  much  magnesia  is  present,  is  still  a  pure 
carbonate  rock.  With  the  impurities  to  be  discussed  in  later 
paragraphs,  however,  this  is  not  the  case.  Silica,  alumina,  iron, 
sulphur,  alkalies,  etc.,  when  present  are  actual  impurities,  not 
merely  chemical  replacements  of  part  of  the  calcium  carbonate. 

The  Presence  of  Silica,  Alumina,  Iron,  and  Other  Impurities. — 
If  a  number  of  limestone  analyses  be  examined,  it  will  be  found 
that  the  principal  impurities  present  are  silica,  alumina,  iron 
oxide,  sulphur,  and  alkalies. 

Silica  when  present  in  a  marble  or  crystalline  limestone  is 
usually  combined  with  alumina,  iron,  lime,  or  magnesia,  and 
occurs  therefore  in  the  form  of  a  silicate  mineral.  In  an  ordinary 
limestone  it  is  very  often  present  as  masses  or  nodules  of  chert 
or  flint,  or  else  combined  with  alumina  as  clayey  matter.  In 
the  softer  limestones,  such  as  the  chalks  and  marls,  the  silica 
may  be  present  as  grains  of  sand. 

Alumina  is  commonly  present  combined  with  silica  either  as 
grains  of  a  silicate  mineral  or  as  clayey  matter. 

Iron  may  be  present  as  carbonate,  as  oxide,  or  in  the  sulphide 
form  as  the  mineral  pyrite. 


154 


BUILDING  STONES  AND   CLAYS 


Sulphur  is  commonly  present  in  small  percentages  in  one  of 
two  forms:  as  pyrite  or  iron  disulphide  (FeS2)  or  as  gypsum  or 
lime  sulphate  (CaS04  +  2  H2O). 

The  alkalies  soda  and  potash  are  frequently  present  in  small 
quantity,  probably  in  the  form  of  carbonates. 

Average  Composition  of  Limestones.  —  On  succeeding  pages 
a  series  of  tables  containing  a  large  number  of  analyses  of  Ameri- 
can limestones  of  commercial  importance  will  be  presented.  Be- 
fore doing  this,  however,  it  is  of  interest  to  endeavor  to  get  some 
idea  of  the  normal  or  average  chemical  composition  of  the  stones 
of  this  group.  Fortunately  a  very  interesting  pair  of  average 
analyses  are  available  for  this  purpose,  and  these  are  reprinted 
here  as  Table  79. 


TABLE  79.  —  AVERAGE  ANALYSES  OF  AMERICAN 
LIMESTONES.     (F.  W.  CLARKE.) 


A. 

B. 

Silica  (SiO2)                   

5.19 

14.09 

Alumina  (A12O3)  *     

0.87 

1.83 

Iron  oxide  (Fe2Os)                                 

0.54 

0.77 

Lime  (CaO)                                      

42.61 

40.60 

7.90 

4.49 

Soda  (Na2O)                             

0.05 

0.62 

Potash  (K2O)                        

0.33 

0.58 

Phosphorus  pentoxide  (P2O5)                        

0.04 

0.42 

Sulphur  (S)                

0.09 

0.07 

Sulphur  trioxide  (SOs)                       

0.05 

0.07 

41.58 

35.58 

0.56 

0.88 

0.21 

0.30 

*  Including  very  small  amounts  of  titanic  oxide  (TiO2). 
f  Including  organic  matter. 

A.  Composite  analyses  of  345  samples  of  American  limestones,  uses  not 

specified.     H.  N.  Stokes,  analyst. 

B.  Composite  analyses  of  498  samples  of  American  limestones  used  for 

building  purposes.     H.  N.  Stokes,  analyst. 


LIMESTONES 


155 


TABLE  80.*  —  ANALYSES  OF  LIMESTONES: 
(BEDFORD  STONE.) 


INDIANA. 


Locality. 

Silica. 

Alumina 
and  Iron. 

Lime  car- 
bonate. 

Magnesium 
carbonate. 

Alkalies. 

Water. 

Bedford 

0  64 

0.15 

98.27 

0.84 

Bedford 

0.50 

0.98 

96.60 

0.27 

0.40 

0.61 

Bedford 

0.63 

0.39 

98.20 

0.39 

Bedford     

1.69 

0.49 

96.79 

0.23 

0.32 

0.41 

Big  Creek 

0  15 

0  64 

93  80 

4  01 

1  09 

Big  Creek 

0  50 

0  71 

93  07 

4  22 

1  19 

Bloomington 

1  74 

0  29 

95  62 

0  89 

0  59 

Bloomington 

1  60 

0  18 

95  55 

0  93 

0  42 

Bloomington 

0  65 

1.00 

95.54 

0.40 

0.55 

0.25 

Harrison  County  
Hunter  Valley 

0.31 
0  86 

0.32 
0  16 

98.09 
98  11 

n.d. 
0  92 

0.40 

0.12 

Romona 

1  26 

0  18 

97  90 

0.65 

Salem  

1.13 

1.06 

96.04 

0.72 

0.15 

0.10 

Spencer  

0.70 

0.91 

96.79 

0.23 

0.32 

0.41 

Stinesvile 

0  90 

3  00 

95.00 

0.22 

0.83 

0.05 

Twin  Creek 

0  76 

0  15 

98  16 

0  97 

*  21st  Ann.  Rep.  Ind.  Dept.  Geol.,  p.  320. 


TABLE  81.*  — ANALYSES  OF  LIMESTONES:  MISSOURI. 


Locality. 

Silica. 

Alu- 
mina 
and  iron 
oxides. 

Lime 
carbon- 
ate. 

Lime. 

Magne- 
sium 
carbon- 
ate. 

Magne- 
sia. 

Carbon 
dioxide. 

Water. 

Bowling  Green 

13  99 

1   62 

49  77 

34  46 

Breckenridge  .... 

2  93 

0  54 

54  22 

0  22 

42  58 

Cape  Girardeau  

0.10 

0  14 

55  73 

0  24 

43  91 

0  27 

Cape  Girardeau  
Carthage  

2.93 
0.69 

0.45 
0.21 

87.23 

98.57 

9.26 
0  65 

De  Soto  

11.19 

0.68 

48.18 

39.99 

Hannibal 

0  26 

0  14 

98  87 

0  62 

Jackson 

4  66 

0  28 

52  29 

0  97 

41  72 

Osceola 

0  99 

0  17 

98  59 

0  09 

Phenix 

0  21 

0  23 

99  06 

0  58 

Princeton  

1  88 

0  78 

96  22 

1  01 

Republic  
Sedalia  

0.45 
17.69 

0.12 
1  08 

49  21 

55.48 

3i  57 

0.03 

43.70 

0.42 

Springfield 

0  36 

0  13 

99  34 

0  22 

Springfield  

4.51 

0.52 

92.24 

2.35 

St.  Louis.  .  . 

0  54 

0  25 

55  42 

0  25 

43  42 

St.  Louis  

2  36 

0  27 

96  09 

0  90 

Kept.  Mo.  Bur.  Geol.,  Vol.  2,  2d  series,  p.  308. 


156 


BUILDING  STONES  AND  CLAYS 


TABLE  82. —  ANALYSES  OF  LIMESTONE:  WISCONSIN. 


1 

2 

3 

4 

5 

6 

Silica 

3  17 

6  32 

0  02 

2  12 

1  09 

0  61 

Alumina         ) 

1  95 

1  02 

0  01 

0  59 

0  33 

(1.97 

Ferric  oxide  ) 
Ferrous  oxide          

\  2.18* 

Lime  carbonate  

49  97 

50.96 

54  74 

53  51 

54  42 

52  48 

Magnesium  carbonate  

44  58 

41.75 

45  07 

43  54 

44  17 

41  94 

*  Fe2C03. 

1.  Duck  Creek;  W.  W.  Daniells,  analyst;  Bull.  4,  Wis.  Geol.  Sur.,  p.  420. 

2.  Genesee;  W.  W.  Daniells,  analyst;  Bull.  4,  Wis.  Geol.  Sur.,  p.  420. 

3.  Knowles;  W.  W.  DanieUs,  analyst;  Bull.  4,  Wis.  Geol.  Sur.,  p.  420. 

4.  Marblehead;  W.  W.  Daniells,  analyst;  Bull.  4,  Wis.  Geol.  Sur.,  p.  420. 

5.  Sturgeon  Bay;  W.  W.  Daniells,  analyst;  Bull.  4,  Wis.  Geol.  Sur.,  p.  420. 

6.  Washburn,  Bayfield  County;  C.  W.  Hall,  analyst;  Min.  Res.  U.  S.,  1903, 

p.  205. 


PHYSICAL  CHARACTERS  AND  TESTS. 

Texture  and  Structure.  —  In  texture  limestones  differ  among 
themselves  even  more  widely  than  do  sandstones,  for  in  addition 
to  differences  in  size  and  shape  of  grain,  there  are  also  important 
structural  differences  to  be  considered.  Many  of  these  points 
of  difference  between  individual  limestones  are  obvious  enough 
when  a  hand  specimen  is  examined,  but  occasionally  differences 
are  only  brought  to  notice  by  the  microscope.  This  last  case  is 
relatively  rare,  however,  and  the  examination  of  thin  sections  of 
limestone  under  the  petrographic  microscope  does  not  often 
yield  enough  information  to  justify  the  trouble  and  expense. 

Color.  —  Limestones  when  absolutely  pure  are  white,  but  as 
actually  found  in  nature  they  show  a  wide  range  of  colors  from 
pure  white  through  yellowish,  bluish,  and  gray  tints  to  deep 
black.  Pink,  reddish,  and  green  limestones  also  occur,  but  in 
these  cases  the  limestone  is  usually  polished  and  marketed  as  a 
marble.  The  commonest  tints  are,  however,  light  gray  and 
grayish-blue.  These  variations  in  color  are  due  to  the  character 
and  amount  of  impurities  present,  the  principal  coloring  agents 
being  organic  matter  and  iron  oxide. 

The  color,  whatever  its  tint,  may  be  uniformly  distributed 
throughout  the  stone,  or  it  may  show  blotching  or  banding  with 


LIMESTONES  157 

two  or  more  tints.  Such  irregular  distribution  of  color  is  un- 
desirable in  an  ordinary  limestone ;  but  if  the  colors  show  pleasing 
contrasts,  and  the  texture  of  the  stone  admits  of  a  good  polish, 
the  material  may  be  valuable  as  a  decorative  marble. 

Varieties  of  Limestone.  —  A  number  of  terms  are  in  general 
use  for  the  different  varieties  of  limestone,  based  upon  differences 
of  origin,  texture,  composition,  etc.  The  more  important  of  these 
terms  will  be  briefly  defined. 

The  marbles  are  limestones  which,  through  the  action  of  heat 
and  pressure,  have  become  more  or  less  distinctly  crystalline. 
The  term  marl  as  at  present  used  in  cement  manufacture  is  ap- 
plied to  a  loosely  cemented  mass  of  lime  carbonate  formed  in  lake 
basins.  Calcareous  tufa  and  travertine  are  more  or  less  compact 
limestones  deposited  by  spring  or  stream  waters  along  their 
courses.  Oolitic  limestones,  so  called  because  of  their  resemblance 
to  a  mass  of  fish-roe,  are  made  up  of  small  rounded  grains  of 
lime  carbonate.  Chalk  is  a  fine-grained  limestone  composed  of 
finely  comminuted  shells,  particularly  those  of  the  foraminifera. 
The  presence  of  much  silica  gives  rise  to  a  siliceous  or  cherty 
limestone.  If  the  silica  present  is  in  combination  with  alumina, 
the  resulting  limestone  will  be  clayey  or  argillaceous. 

Physical  Characters  of  Limestones.  —  In  texture,  hardness, 
and  compactness  the  limestones  vary  from  the  loosely  consoli- 
dated marls  through  the  chalks  to  the  hard,  compact  limestones 
and  marbles.  Parallel  with  these  variations  are  variations  in 
absorptive  properties  and  density.  The  chalky  limestones  may 
run  as  low  in  specific  gravity  as  1.85,  corresponding  to  a  weight 
of,  say,  110  pounds  per  cubic  foot,  while  the  compact  limestones 
commonly  used  for  building  purposes  range  in  specific  gravity 
between  2.3  and  2.9,  corresponding  approximately  to  a  range 
in  weight  of  from  140  to  185  pounds  per  cubic  foot. 


TABLE  83.  — COMPRESSIVE  STRENGTH  OF  AMERICAN 
LIMESTONES. 


State. 

Locality. 

Tested  by 

"3 
6 

fc 

Size  of  cube. 

Compressive  strength, 
pounds  per  square  inch. 

Min. 

Aver. 

Max. 

Arkansas 

Illinois 
Indiana 

Kentucky 
Missouri 

New  York 
Texas 

Wisconsin 

Eureka  Springs,  Carroll  Co. 
Beaver,  Carroll  Co 

Watertown  Arsenal 
Navy  Department 
Ark.  Indust.  Inst. 

Univ.  Illinois 
Watertown  Arsenal 

Rose  Polytech.  Inst. 

Watertown  Arsenal 
Missouri  Geol.  Sur. 

Watertown  Arsenal 
Rock  Island  Arsenal 

Un  v.  of  Texas 
Wisconsin  Geol.  Sur. 

Univ.  of  Wisconsin 
Wisconsin  Geol.  Sur. 

In. 

21,397 
20,581 
15,550 

13,544 
14  120 

Johnson,  Carroll  Co  

Kankakee,  Kankakee  Co.  .  . 
Niota,  Hancock  Co  

Ellettsville  
Salem 

"3' 
3 
3 
3 
3 
3 
3 
3 
3 
3 
3 
3 

3 
6 

4 
11 
3 
2 
2 
4 
10 
2 
5 
7 
7 
4 
4 
4 
4 
6 
4 
6 
4 
4 
3 
2 
7 

2 

"f 

4 
4 

4 
5 

4 
4 
4 
4 
4 
4 
4 
4 
4 
4 
4 
4 
4 
4 
4 
4 
4 
4 
4 
4 
4 
4 
4 

4 

5,900 
5,900 
8,400 
3,400 
6,400 

6,900 
11,700 
11,400 
4,600 
7,800 

Bloomington 

Hunter  Valley  
Romona 

Bedford  

3,400 
3,300 
6,400 
4,400 
4,700 
4,500 
5,800 
4,100 

6,532 
5,656 

13,660 

6,800 
4,800 
9,700 
6,900 
8,200 
7,500 
6,200 
6,600 

7,009 
",425 

17,130 
20,261 
10,721 
8,267 
10,290 
18,575 
10,679 
29,306 
14,102 
19,751 
12,582 
12,544 
13,124 
12,985 
25,360 
14,176 
13,013 
12,704 
10,071 
14,053 
13,140 
22,438 
17,149 

28,951 

Stinesville.  . 

6,035 
5,635 

6,762 
6,692 

14,947 
15,282 
8,792 
6,944 
9,829 
15,980 
9,214 
27,813 
11,870 
16,319 
11,545 
11,260 
11,198 
12,641 
24,662 
12,062 
11,270 
8,705 
8,486 
12,995 
10,453 
20,779 
15,063 

23,724 
3,422 

Bowling  Green,  Warren  Co.  . 
Caden,  Warren  Co  

Carthage                           

Bowling  Green  

Breckenridge 

Columbia  

De  Soto  

Hannibal  .  .  . 

Joplin   .         

Jefferson  City  . 

Kahoka 

Koeltztown  
Noel                               .     . 

Phenix 

Pierce  City  

Rolla  

Sedalia  .  .            

Sheffield 

Springfield  

St  Louis               

18,496 

Buffalo 

Duval  

8207 

2,279 
6,303 
14,950 
18,660 
9,228 
2,300 
1,495 
3,180 

"20,326' 
12,255 

4 

4 
1 
1 

1 
1 

.... 

1 
1 

"2 
"2 

9 

14,545' 
7,305 

Honey  Creek,  Burnet  Co..  .  . 
Slaughter  Creek  . 

Bear  Creek  

Cedar  Park  
Round  Rock 

Lueders,  Jones  Co  

6,675 
'  23,783' 

2,487 

8,394 
12,066 
24,283 
8,830 
36,731 
29,189 

10,112 
"24,783' 

Duck  Creek 

Genesee              

Knowles 

"e" 

'  '29,526' 

31,936 
42,787 
30,941 
19,234 
18,379 

'  31,957' 

"w.iii" 

Myrblehead       

Waukesha  

Wauwatosa        

17,647 

(158) 


LIMESTONES 


159 


TABLE   84.  —  PHYSICAL  TESTS  OF  LIMESTONES:  ENGLAND. 

(BEARI.) 


Locality. 

Specific 
gravity. 

Weight  per 
cubic  foot. 

Absorption, 
per  cent. 

Compressive 
strength, 
pounds  per 
square  inch. 

White  Man's  Field 

2  245 

140.1 

5.01 

7,185 

Red  Man's  Field                  

2.295 

143.2 

4.58 

9,210 

Yellow  Man's  Field  

2.33 

145.4 

4.62 

8,980 

Anston  

2.117  - 

132.2 

7.50 

4,700 

Ancaster  

(2.25 

140.4 

6.27 

2,860 

Portland                        .                ... 

|  2.505 
(2.205 
<  1  .  995 

156.3 
137.6 
124  5 

2.42 
6.84 
11.10 

8,595 
4,465 

2,285 

Ketton 

(  2.120 
2.05 

132.3 
127.9 

7.51 
8.10 

3,190 
1,585 

D 

2  80 

174  7 

14875 

Corsham  Down  

2.067 

129.0 

11.12 

1,705 

Farleigh  Down  

1.93 

120.5 

12.88 

1,010 

Monks  Park 

2  19 

136  7 

8  03 

2,255 

Box  Ground..    . 

2  05 

127  9 

7  79 

1,515 

Coombe  Down 

2  06 

128  6 

5  99 

2,005 

Corngrit        

2  14 

133  6 

8  88 

2,185 

Stoke  Ground  

2.023 

126  3 

10  85 

1,540 

Winsley  Ground  

2.13 

132  9 

7  74 

1,660 

Westwood  Ground 

(2.12 

132.3 

8.03 

1,735 

Doulting  .  . 

(  2.087 
(  2.41 

130.3 
150.4 

8.85 
3.36 

1,910 
2,815 

Ham  Hill 

I  2.003 
2  18 

125.0 
136  0 

10.87 
? 

1,735 
2  585 

DISTRIBUTION  AND  PRODUCTION. 

Geologic  and  Geographic  Distribution  of  Limestones.  —  Lime- 
stones occur  in  every  state  and  territory  in  the  United  States, 
though  of  course  some  states  (Delaware,  North  Dakota,  Louisi- 
ana, etc.)  are  so  poorly  supplied  that  they  can  never  become 
important  lime  producers,  while  other  states  are  almost  entirely 
underlain  by  limestone  strata.  Geologically,  the  limestone 
utilized  in  various  parts  of  the  United  States  ranges  entirely 
through  the  geological  column,  from  the  pre-Cambrian  to  the 
Pleistocene,  inclusive. 

Under  such  conditions  of  wide  geographic  and  geologic  distri- 
bution it  is  not  practicable  to  give  a  summary  of  any  value  in 
the  present  volume.  The  list  of  references  given  in  the  follow- 
ing pages  will  enable  the  reader  to  ascertain  the  facts  regarding 
the  limestones  of  any  given  state  in  which  he  may  be  interested. 


160  BUILDING  STONES  AND  CLAYS 

Reference  List  for  Limestones: 

Alabama: 

McCalley,  H.     The  fluxing  rocks  of  Alabama.     Eng.  and  Min.  Journal, 

vol.  63,  pp.  115,  116.     1897. 

Meissner,  C.  A.     Analyses  of  limestones  and  dolomites  of  the  Birmingham 
district.      Proc.  Alabama  Industrial  and  Scientific  Society,  vol.  4, 
pp.  12-23.     1894. 
California: 

Jackson,    A.    W.     Building  stones  of   California.     7th   Annual    Report 

California  State  Mineralogist,  pp.  206-217.     1888. 
Colorado: 

Lakes,  A.     Building  and  monumental  stones  of  Colorado.     Mines  and 

Minerals,  vol.  22,  pp.  29,  30.     1901. 
Lakes,     A.     Sedimentary    building-stones    of    Colorado.     Mines    and 

Minerals,  vol.  22,  pp.  62-64.     1901. 
Connecticut: 

Ries,  H.     The  limestone  quarries  of  eastern  New  York,  western  Vermont, 
Massachusetts,  and  Connecticut.     17th  Ann.  Report  U.  S.  Geological 
Survey,  pt.  3,  pp.  795-811.     1896. 
Georgia: 

McCallie,  S.  W.     A  preliminary  report  on  the  marbles  of  Georgia.     Bull. 

No.  1,  Georgia  Geological  Survey,  92  pp.     1894. 
Indiana: 

Foerste,  A.  F.     A  report  on  the  Niagara  limestone  quarries  of  Decatur, 
Franklin,   and   Fayette  counties.      22d  Ann.   Rep.   Indiana  Dept. 
Geology  and  Natural  Resources,  pp.  195-255.     1898. 
Hopkins,  T.  C.,  and  Siebenthal,  C.  E.     The  Bedford  oolitic  limestone  of 
Indiana.     21st  Ann.   Rep.    Indiana    Dept.    Geology    and    Natural 
Resources,  pp.  291-427.     1897. 
Iowa: 

Bain,   H.   F.     Properties  and  tests  of  Iowa  building-stones.      Reports 

Iowa  Geological  Survey,  Vol.  8,  pp.  367-416.     1898. 
Houser,   G.  L.     Some  lime-burning  dolomites  and   dolomitic   building 
stones  from  the  Niagara  of  Iowa.     Reports  Iowa  Geological  Survey, 
Vol.  1,  pp.  199-207.     1892. 


Bailey,  E.  H.  S.,  and  Case,  E.  C.     On  the  composition  of  some  Kansas 

building-stones.     Trans.  Kansas  Academy  Science,  vol.  13,  p.  78. 
Kentucky: 

Crump,  H.  M.     The  clays  and  building  stones  of  Kentucky.     Eng.  and 

Mining  Journal,  vol.  66,  pp.  190,  191.     Aug.  13,  1898. 
Maryland: 

Matthews.     An  account  of  the  character  and  distribution  of  Maryland 
building  stones,  together  with  a  history  of  the  quarrying  industry. 
Reports  Maryland  Geological  Survey,  Vol.  2,  pp.  125-241.     1898. 
Massachusetts: 

Ries,  H.  The  limestone  quarries  of  eastern  New  York,  western  Vermont, 
Massachusetts,  and  Connecticut.  17th  Ann.  Rep.  U.  S.  Geol.  Survey, 
pt.  3,  pp.  795-811.  1896. 


LIMESTONES  161 

Michigan: 

Benedict,  A.  C.     The  Bayport  (Mich.)  quarries.     Stone,  vol.  17,  pp. 

153-164.     1898. 
Grabau,  A.  W.     Stratigraphy  of  the  Traverse  group  of  Michigan.     Ann. 

Report  Michigan  Geological  Survey  for  1901,  pp.  161-210.     1902. 
Lane,  A.  C.     Michigan  limestones  and  their  uses.     Eng.  and  Mining 

Journal,  vol.  71,  pp.  662,  663,  693,  694,  725.     1901. 
Lane,  A.  C.     Limestones  (of  Michigan).     Ann.  Rep.  Mich.  Geol.  Survey 

for  1901,  pp.  139-160.     1902. 
Lane,  A.  C.     Limestones  (of  Michigan).     Ann.  Rep.  Mich.  Geol.  Survey 

for  1902,  pp.  17-19.     1903. 
Minnesota: 

Winchell,  N.    H.     The   building  stones   of   Minnesota.       Final    Report 

Geology  of  Minnesota,  Vol.  1,  pp.  142-204.     1884. 
Missouri: 

Buckley,  E.  R.     Quarry  industry  of  Missouri.     Bull.  2,  Missouri  Geo- 
logical Survey,  1904. 
Nebraska: 

Fisher,  C.  A.     Directory  of  the  limestone  quarries  of  Nebraska.     Ann. 
Rep.  for  1901,  Nebraska  State  Board  of  Agriculture,  pp.  243-247. 
1902. 
New  Jersey: 

Cook,  G.  H.,  and  Smock,  J.  C.     New  Jersey  building  stones.     Reports 

10th  Census,  Vol.  10,  pp.  139-146.     1884. 

Nason,  F.  L.     The  chemical  composition  of  some  of  the  white  limestones 
of  Sussex  County,  New  Jersey.     American  Geologist,  vol.  13,  pp. 
154-164.     1894. 
New  York: 

Bishop,  I.  P.     Structural  and  economic  geology  of  Erie  County,  N.  Y. 

15th  Ann.  Rep.  N.  Y.  State  Geologist,  vol.  1,  pp.  305-392.     1897. 
Eckel,  E.  C.     The  quarry  industry  in  southeastern  New  York.     20th 

Ann.  Rep.  N.  Y.  State  Geologist,  pp.  141-176.     1902. 
Lincoln,  D.  F.     Report  on  the  structural  and  economic  geology  of  Seneca 
County,  N.  Y.    14th  Ann.  Rep.  New  York  State  Geologist,  pp.  60-125. 
1897. 

Ries,  H.     The  limestone  quarries  of  eastern  New  York,  western  Vermont, 
Massachusetts,  and  Connecticut.     17th  Ann.  Rep.  U.  S.  Geological 
Survey,  pt.  3,  pp.  795-811.     1896. 
Ries,  H.     Limestones  of  New  York  and  their  economic  uses.     17th  Ann. 

Rep.  N.  Y.  State  Geologist,  pp.  355-468.     1899. 
Ries,  H.     Lime  and  cement  industries  of  New  York.     Bull.  44,  N.  Y. 

State  Museum.     1903. 
Smock,  J.  C.     Building  stones  in  the  state  of  New  York.     Bull.  3,  N.  Y. 

State  Museum,  152  pp.     1888. 
Smock,  J.  C.     Building  stones  in  New  York.     Bull.  10,  N.  Y.  State 

Museum,  396  pp.    1890. 
Oklahoma: 

Gould,   C.   N.     Oklahoma  limestones.     Stone,   vol.   23,     pp.   351-354. 
1901. 


162 


BUILDING  STONES  AND  CLAYS 


Pennsylvania: 

Frear,  W.     The  use  of  lime  on  Pennsylvania  soils.     Bull.  61,  Penna. 

Dept.  Agriculture,  170  pp.     1900. 
South  Dakota: 

Todd,  J.  E.     The  clay  and  stone  resources  of  South  Dakota,  Eng.  and 

Mining  Journal,  vol.  66,  p.  371.     1898. 
Tennessee: 

Cotton,  H.  E.,  and  Gattinger,  A.     Tennessee  building  stones.     Reports 

Tenth  Census,  Vol.  10,  pp.  187,  188.     1884. 
Keith,  H.     Tennessee  marble.     Bull.  213,  U.  S.  Geol.  Survey,  pp.  366- 

370.     1903. 
Texas: 

Durable,    E.    T.     Building   and   ornamental   stones   of   Texas.     Stone, 

May,  1900. 
Vermont: 

Perkins,  G.  H.     Report  on  the  marble,  slate,  and  granite  industries  of 

Vermont.     68  pp.     Rutland,  1898. 
Perkins,   G.   H.     Limestone  and  marble  in  Vermont.     Rep.   Vermont 

State  Geologist  for  1899-1900,  pp.  30-57.     1900. 

Ries,  H.     The  limestone  quarries  of  eastern  New  York,  western  Vermont, 
Massachusetts,    and   Connecticut.     17th   Ann.    Rep.    U.    S.    Geol. 
Survey,  pt.  3,  pp.  795-811.     1896. 
Wisconsin: 

Buckley,  E.  R.     Building  and  ornamental  stones  of  Wisconsin.     Bull.  4, 

Wisconsin  Geol.  Survey,  500  pp.     1898. 
Wyoming: 

Knight,  W.  C.     The  building-stones  and  clays  of  Wyoming.     Eng.  and 
Mining  Journal,  vol.  66,  pp.  546,  547.     1898. 


Production  of  Limestone  in  the  United  States.  —  The  follow- 
ing tables,  quoted  from  those  annually  published  by  the  United 
States  Geological  Survey,  contain  statistics  on  the  American 
limestone  industries  for  a  series  of  years. 

TABLE  85.  —  LIMESTONE  PRODUCTION  OF  THE  UNITED 
STATES,    1899-1909. 


Year. 

Value. 

Year. 

Value. 

1899 

$13,889,302 

1905 

$26,025,210 

1900 

13,556,523 

1906 

27,327,142 

1901 

18,202,843 

1907 

31,737,631 

1902 

20,895,385 

1908 

27,682,002 

1903 

22,372,109 

1909 

32,070,401 

1904 

22,178,964 

1910 

34,603,678 

LIMESTONES 


163 


TABLE    86.  — LIMESTONE  PRODUCTION,   BY  STATES,   1905-1909. 


State  or  Territory. 

1905. 

1906. 

1907. 

1908. 

1909. 

Alabama 

$532,103 

$579,344 

$694,699 

$479,730 

$700,642 

Arizona  

135 

40 

64,975 

a  50,130 

(b) 

Arkansas  
California 

154,818 
49,902 

48,844 
80,205 

52,207 
177,333 

61,971 
237,320 

112,468 
283,869 

Colorado  
Connecticut 

289,920 
1,558 

373,158 
1,171 

502,751 
1,476 

378,822 
c  3,727 

355,136 
c  5,023 

Florida  

5,800 

1,450 

15,000 

41,910 

d  49,856 

Georgia  
Hawaii 

9,030 

16,042 

22,278 

8,495 

34,593 
(e) 

Idaho  

14,105 

12,600 

15,900 

36,000 

(e) 

Illinois  
Indiana  

3,511,890 
3,189,259 

2,942,331 
3,725,565 

3,774,346 
3,624,126 

3,122,552 
3,643,261 

4,234,927 
3,749,239 

Iowa  
Kansas 

451,791 
923,389 

493,815 
849,203 

560,582 
813,748 

530,945 
403,176 

525,277 
892  335 

Kentucky  

744,465 

795,408 

891,500 

810,190 

903,874 

Louisiana  .  .          .              ... 

(/) 

Maine  

7,428 

2,000 

1,350 

(g) 

(g) 

Maryland  
Massachusetts 

149,402 
65,908 

170,046 
10,750 

142,825 
1  837 

128,591 
1  950 

197,939 

Michigan  

544,754 

656,269 

760,333 

669,017 

750,589 

Minnesota  

555,401 

632,115 

735,319 

667  095 

698  309 

Missouri 

2  238  164 

1  988  334 

2  153  917 

2  130  136 

2  111  283 

Montana  
Nebraska 

103,123 
225  119 

141,082 
276  381 

124,690 
312  630 

134,595 
330  570 

154,064 
293  830 

New  Jersey  
New  Mexico  .  .  . 

147,353 
7,200 

221,141 
125,493 

274,452 
193  732 

172,000 
(A) 

224,017 
t  140  801 

New  York  

1,970,968 

2,204,724 

2,898,520 

2,584,559 

2,622,353 

North  Carolina.  .  . 

16,500 

30,583 

22,328 

0) 

0') 

Ohio  . 

2  850  793 

3  025  038 

3  566  822 

3  519  557 

4  020  046 

Oklahoma  

168,924 

171,983 

189,568 

257  066 

450  055 

Oregon  

8,600 

7480 

5  750 

6  230 

Pennsylvania 

4  499  503 

4  865  130 

5  821  275 

4  057  471 

5  073  825 

Rhode  Island  

300 

678 

750 

(g) 

(g) 

South  Dakota 

6  653 

10  400 

11  600 

(k) 

I  49  328 

Tennessee  

401,622 

481,952 

385  450 

m  535  882 

m  589  949 

Texas.  .  . 

171  847 

239  125 

267  757 

314  571 

341  528 

Utah 

232  519 

248  868 

306  344 

253  088 

169  700 

Vermont  
Virginia 

11,095 
212  660 

14,728 
260  343 

23,126 
362  062 

20,731 
280  542 

18,839 
342  656 

Washington  

52,470 

49,192 

62317 

31  660 

38  269 

West  Virginia.... 

671  318 

628  602 

855  941 

645  385 

864  392 

Wisconsin 

804  081 

891  746 

1  027  095 

1  102  009 

1  047  044 

Wyoming  

23,340 

53  783 

18  920 

n  31  168 

24  346 

Total  

26,025,210 

27,327,142 

31,737,631 

27,682,002 

32,070,401 

a  Includes  New  Mexico. 

6  Included  in  New  Mexico. 

c  Includes  Maine  and  Rhode  Island. 

d  Includes  Louisiana. 

e  Included  in  South  Dakota. 

/  Included  in  Florida. 

0  Included  with  Connecticut. 


h  Included  with  Arizona. 
i  Includes  Arizona. 
j  Included  with  Tennessee, 
ik  Included  with  Wyoming. 
I  Includes  Hawaii  and  Idaho. 
m  Includes  North  Carolina, 
n  Includes  South  Dakota. 


164 


BUILDING  STONES  AND  CLAYS 


TABLE  87.  — LIMESTONE  PRODUCTION,   BY  STATES  AND 

USES,  1909. 


State  or  Territory. 

Rough 
building. 

Dressed 
building. 

Paving. 

Curbing. 

Flagging. 

Rubble. 

Riprap. 

Alabama 

$775 

$27  197 

$2  000 

$46  115 

$8  460 

$19  200 

Arkansas  

23,655 

74,413 

650 

California 

12,341 

Connecticut  

90 

Florida  

6,955 

684 

14,400 

Georgia 

954 

Illinois  
Indiana  
Iowa  

62,395 
1,235,524 
41,866 

34,323 
1,353,180 
7,765 

2,600 
534 

4,348 
109,454 
420 

$4,651 
4,921 

368,605 
14,100 
49,947 

115,413 
7,939 
43,094 

Kansas  .' 
Kentucky 

75,574 
130,784 

43,775 
63,844 

22,044 
4,583 

160 
16  313 

493 
219 

58,519 
6  596 

41,984 
20,081 

Maryland  
Michigan 

4,413 
4,450 

7,445 

600 

10 

1,572 

1,500 
3,615 

Minnesota 

169,929 

96809 

5  697 

5  031 

94453 

42  666 

Missouri  

233,215 

408,327 

1,531 

2,354 

10,374 

301,463 

106,419 

Montana 

7,628 

333 

Nebraska  

1,507 

1,033 

12,926 

28,645 

New  Jersey       

375 

540 

New  York  

168,569 

37,355 

3,080 

2,574 

315 

83,198 

63,526 

Ohio  
Oklahoma 

102,109 
4,850 

31,133 
1,000 

624 

180 

27,675 
4,459 

430,789 
35,889 

Pennsylvania  

104,930 

1,410 

124,521 

2,128 

1,250 

2,283 

709 

Tennessee  

16,854 

4,432 

3,310 

4,085 

26,298 

Texas 

28,601 

17540 

365 

60 

86,241 

14,581 

Utah 

29  785 

Vermont 

5,412 

Virginia  
Wisconsin 

715 
96,161 

129 

15,832 

15 

26,807 

20,573 

7 
13,902 

3,000 
97,689 

""65,063' 

Wyoming 

700 

Total  

2,570,326 

2,226,942 

188,680 

214,140 

41,343 

1,228,445 

1,082,234 

LIMESTONES 


165 

is 


TABLE  87.  — LIMESTONE  PRODUCTION,  BY  STATES  AND 
USES,  1909.  —  Continued. 


State  or  Territory. 

Crushed  stone. 

Flux. 

Sugar, 
factories. 

Other. 

Total. 

Road 
making. 

Railroad 
ballast. 

Concrete. 

Alabama 

$60,452 

$5,521 

$16,825 

$512,585 

$1,512 

$700,642 
(a) 
112,468 
283,869 
355,136 
6  5,023 
c  49,856 
34,593 
(d) 

w 

4,234,927 
3,749,239 
525,277 
892,335 
903,874 
(e) 
CO 
197,939 
750,589 
698,309 
2,111,283 
154,064 
293,830 
224,017 
g  140,801 
2,622,353 

w 

4,020,046 
450,055 
5,073,825 
(/) 
t  49,328 
j  589,949 
341,528 
169,700 
18,839 
342,656 
38,269 
864,392 
1,047,044 
24,346 

Arkansas  
California  

9,126 
138,962 
100 

340 

4,284 
4,554 

29,904 
267,806 
1,933 

"'15,696' 

$92,233 
86,888 

5,875 
342 
3,000 
8,755 

Connecticut       .  . 

Florida  
Georgia  
Hawaii 

4,150 

749 

2,569 
14,091 

12,343 
3,103 

Idaho 

Illinois     

1,216,759 
627,289 
116,246 
155,294 
273,411 

422,859 
54,086 
16,329 
257,654 
291,266 

1,249,783 
54,449 
246,054 
207,405 
47,364 

714,631 
190,809 

1,971 
982 
675 

36,589 
95,972 

2,881 
28,940 
38,609 

Indiana 

Iowa  
Kansas 

493 
10,804 

Kentucky  
Louisiana 

Maine 

Maryland  
Michigan 

108,630 
132,902 
80,441 
542,904 

"'83,i47' 
8,321 
3,750 
750,980 

'1,502,483" 
5,491 
596,023 

20,071 
42,445 
38,329 
87,445 

'"31,898 

61,201 
112,829 
157,263 
339,036 
15,400 
118,523 
8,346 
3,150 
495,970 

"236,6i9' 
243,277 
489,241 

"5',406' 
72,706 
24,260 

'"'oi'.ois' 
""31,675 

127,532 
15,000 
206,435 
15,395 
343,891 

'1,130,682' 
3,165,872' 

"i',266' 
87,432 
40,819 
126,915 
250 
213,444 
31,317 
492,497 
56,075 

""25,845' 
6,033 
13,321 
3,171 
1,136 

1,514 
327,571 
1,658 
33,819 

'"i5 

"ii',606 
253,406 

Minnesota  
Missouri 

Montana  
Nebraska 

New  Jersey  

New  Mexico  

107,500 
419,489 

"332,569' 
148,589 
444,091 

New  York  
North  Carolina  
Ohio 

2,088 

223,695 
6,500 
140,767 

Oklahoma  
Pennsylvania  
Rhode  Island  

'22,944' 

South  Dakota  
Tennessee  

7,184 
276,945 
125,661 

12,600 
95,665 
3,400 

2,222 

Texas  
Utah 

13,000 

"'143' 
1,319 
6,727 
9,940 
7,021 
2,646 

Vermont  
Virginia 

8,672 
31,076 
225 
47,152 
379,723 

'"84,883" 

"294,  938' 
79,803 

4,362 
8,068 

"19,865' 
188,395 

Washington.  
West  Virginia  

Wisconsin  

""2l',666' 

Wyoming    

Total  

7,294,248 

3,308,430 

4,450,075 

7,921,807 

291,287 

1,252,444 

32,070,401 

a  Included  in  New  Mexico. 

b  Includes  Maine  and  Rhode  Island. 

c  Includes  Louisiana. 

d  Included  in  South  Dakota. 

e  Included  in  Florida. 


/  Included  in  Connecticut. 

g  Includes  Arizona. 

h  Included  in  Tennessee. 

i  Includes  Idaho  and  Hawaii. 

3  Includes  North  Carolina. 


CHAPTER  X. 
MARBLES. 

THE  term  marble  is  applied  by  the  geologist  to  limestones 
which,  through  the  action  of  heat  and  pressure,  have  so  changed 
in  texture  as  to  be  completely  crystalline,  n  In  the  stone  trade,  \ 
however,  marble  has  a  wider  meaning,  including  any  limestone 
which  can  be  made  to  take  a  high  polish  and  which,  when  so 
polished,  will  show  pleasing  color  effects.  Indeed  the  term  has 
at  times  been  carelessly  applied  even  to  siliceous  rocks,  a  mis- 
application which  entirely  robs  it  of  meaning. 

Varieties  of  Marble.  —  Using  the  term  marble  in  the  sense  in 
which  it  is  applied  by  the  engineer  and  quarryman,  three  quite 
distinct  types  may  be  noted. 

(a)  Highly   crystalline   marbles   showing   distinct   crystalline 
structure  and  fracture.     These  are  usually  white,  though  gray, 
black,  or  other  markings  may  be  present,  scattered  over  a  white 
ground.     Most  of  the  Alabama,  Georgia,  Vermont,  Massachusetts, 
Connecticut,  and  southeastern  New  York  marbles  are  of  this  type. 

(b)  Subcrystalline  or  fossiliferous  marbles;  in  which  crystalline 
structure  is  rarely  very  noticeable,  the  value  depending  rather 
on  color  effect  than  on  texture.     Frequently  these  color  effects 
are  gained  through  the  presence  of  fossils,  as  often  shown  in  the 
Tennessee  marbles. 

(c)  Onyx  marbles;  translucent  rocks,  showing  color  banding, 
due  to  the  fact  that  they  were  formed  layer  after  layer  by  chemi- 
cal deposition  from  spring  or  cave  waters. 

I.  HIGHLY  CRYSTALLINE  MARBLES. 

In  a  sense,  practically  all  limestones  are  crystalline,  for  under 
the  microscope  traces  at  least  of  crystalline  structure  can  be 
detected  even  in  the  most  earthy  limestones.  But  the  stones 
which  are  here  grouped  as  the  highly  crystalline  marbles  are 
crystalline  in  a  much  greater  degree,  for  they  are  made  up  entirely 
of  grains  of  calcite  or  more  rarely  dolomite,  and  the  crystalline 

166 


MARBLES  167 

character  of  these  component  grains  is  obvious,  even  without 
the  use  of  the  microscope. 

Origin  and  Character.  —  The  present  highly  crystalline  con- 
dition of  these  marbles  is  not  due  to  anything  in  their  chemical 
composition,  or  to  the  conditions  under  which  they  were  origi- 
nally deposited,  but  to  the  effects  of  the  heat  and  pressure  to 
which  they  have  been  subjected  since  deposition.  Originally 
they  were  simply  limestones  of  quite  ordinary  type  so  far  as 
either  composition  or  structure  were  concerned,  and  under  normal 
conditions  they  would  have  remained  ordinary  limestones  to 
this  day. 

If  limestones  are  heated  sufficiently  under  atmospheric  pres- 
sure, they  will  simply  be  calcined,  carbon  dioxide  being  driven 
off  and  quicklime  remaining.  But  if  the  heat  be  accompanied 
by  intense  pressure,  sufficient  to  prevent  the  evolution  of  the 
carbon  dioxide  gas,  the  stone  will  assume  a  semifluid  condition. 
This  condition  permits  a  gradual  movement,  rearrangement,  and 
recrystallization  of  the  particles  of  calcite;  and  if  this  meta- 
morphism  is  thorough  enough,  the  final  result  is  the  production 
of  a  highly  crystalline  marble. 

On  a  later  page  in  discussing  the  geological  distribution  of 
the  highly  crystalline  marbles,  some  consideration  will  be  given 
to  the  geological  conditions  which  in  certain  parts  of  the  coun- 
try favored  the  formation  of  these  rocks  in  the  fashion  above 
described. 

Chemical  Composition.  —  Since  the  crystalline  marbles  are 
merely  ordinary  limestones  physically  altered  by  the  action  of 
heat  and  pressure,  they  may  naturally  be  expected  to  show  the 
same  range  in  composition  as  would  a  series  of  normal  limestones. 
If  we  could  make  an  average  analysis  of  all  the  crystalline  lime- 
stones of  the  country,  and  compare  this  with  an  average  analysis 
of  all  the  unaltered  limestones,  this  expectation  would  undoubt- 
edly be  verified. 

The  actual  requirements  of  the  stone  trade,  however,  introduce 
conditions  which  interfere  with  this  exact  agreement  in  composi- 
tion of  the  two  groups,  as  we  find  them  in  the  market.  This  is 
due  to  the  fact  that  the  more  impure  crystalline  marbles,  formed 
by  the  alteration  of  siliceous  and  clayey  limestones,  are  rarely 
suitable  for  dressing  and  polishing.  The  silica  and  clay  of  the 
original  limestone  have  often,  during  the  metamorphism,  com- 


168  BUILDING  STONES  AND   CLAYS 

bined  with  some  of  the  lime  to  form  silicate  minerals,  and  the 
irregular  distribution  of  these  minerals  through  the  marble  inter- 
feres with  its  dressing  and  decreases  the  attractiveness  of  its 
appearance. 

The  result  of  this  condition  is  that  the  highly  crystalline 
marbles  which  have  attained  success  in  the  market  are  rarely 
very  impure.  A  series  of  marble  analyses,  therefore,  tends  to 
give  a  higher  average  lime  content  than  does  a  series  of  analyses 
of  ordinary  limestones. 


MARBLES 


169 


Carbon 
dioxide 


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170 


BUILDING  STONES   AND  CLAYS 


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MARBLES 


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172 


BUILDING  STONES  AND  CLAYS 


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174 


BUILDING  STONES  AND  CLAYS 


Production  of  Marble  in  the  United  States.  —  The  following 
tables,  quoted  from  those  issued  annually  by  the  United  States 
Geological  Survey,  give  statistics  concerning  the  American 
marble  industry  for  a  series  of  years.  It  is  to  be  noted  that  under 
the  head  of  marble  these  tables  include  the  comparatively  unim- 
portant amounts  of  serpentine,  "  verd  antique  marble,"  etc., 
produced  in  the  United  States. 

TABLE  90.  —  MARBLE  PRODUCTION  OF  THE  UNITED 
STATES,   1899-1909. 


Year. 

Value. 

Year. 

Value. 

1899 

$4,011,681 

1905 

$7,129,071 

1900 

4,267,253 

1906 

7,582,938 

1901 

4,965,699 

1907 

7,837,685 

1902 

5,044,182 

1908 

7,733,920 

1903 

5,362,686 

1909 

6,548,905 

1904 

6,297,835 

1910 

6,992,779 

TABLE  91.  — MARBLE  PRODUCTION,   BY  STATES  AND 

USES,  1908-1909. 


1908. 


Rough. 

] 

Dressed 

State  or  Terri- 
tory. 

Build- 
ing. 

Monu- 
mental. 

Other 
uses. 

Build- 
ing. 

Orna- 
mental. 

Orna- 
men- 
tal. 

Interior 
decora- 
tion. 

Other 
uses. 

Total. 

$898 

$2  500 

$113 

$4  650 

$77  000 

$33,419 

a  $118,580 

Alaska..  

38,500 
8,100 

$1,688 
1,250 

45,000 

7,200 

$500 

10,600 
50,782 

400 
276 

6  103,888 
60,408 

Colorado 

c 

Georgia  
Kentucky 

368,981 

342,000 

78,800 

100,000 

17,500 

9,000 

916,281 
d 

1  050 

8425 

4  652 

65,190 

e  79,317 

Massachusetts. 

1,888 

110,856 

19,786 

34,660 

8,458 

175,648 
d 

c 

New  York 

74,538 

56,200 

30,421 

472,407 

53,292 

20,000 

706,858 

North  Carolina 

/ 

Pennsylvania.  . 
Tennessee  
Utah 

13,444 
83,764 

10,755 

'  37',575 

54,803 
78,440 

9,000 
17,590 

7,000 

15,000 
551,449 

3,500 
10,660 

102,747 
790,233 
c 

Vermont  

156,325 

134,036 

190 

1,402,629 

1,714,408 

18,006 

1,184,259 

70,107 

4,679,960 

Total.... 

747,488 

554,354 

154,138 

2,329,438 

1,843,426 

25,506 

1,943,750 

135,820 

7,733,920 

a  Includes  Kentucky  and  Missouri. 

b  Includes  Colorado,  New  Mexico,  and  Utah. 

c  Included  in  Alaska. 


d  Included  in  Alabama. 
e  Includes  North  Carolina. 
/  Included  in  Maryland. 


MARBLES 


175 


TABLE  91.  — MARBLE  PRODUCTION,  BY  STATES  AND 

USES,  190&-1909.  —  Continued. 


1909. 


State  or  Terri- 
tory. 

Rough. 

Dressed. 

Total. 

Build- 
ing. 

Monu- 
mental. 

Other 
uses. 

Build- 
ing. 

Monu- 
mental. 

Orna- 
men- 
tal. 

Interior 
decora- 
tion. 

Other 
uses. 

Alabama  
Alaska  

$39,825 
42,100 

83,887 
190,600 
528,454 

$22,783 
300 

$6,900 
500 

$12,000 

$129,554 

$1,400 

a  $212,462 
6  46,900 

89,392 
d  488,311 
766,449 
e' 

243,711 
/  5,390 
402,729 
e 

186,037 
613,741 
c 

3,493,783 
h 
e 

$4,000 

California  
Colorado  
Georgia  •  
Kentucky 

563 
175 

25,000 

4,942 
'  15,745 

156,666 

2,045 
26,250 

295,491 

15,000 

Maryland.  .  .  . 
Massachusetts 
New  Mexico  .  . 
New  York... 
North  Carolina 
Oregon  
Pennsylvania. 
Tennessee  
Texas  
Utah  
Vermont  
Washington  .  .  . 
West  Virginia 

23,759 
500 
64,400 

900 
2,950 
49,950 

1,424 
940 
32,641 

16,500 
1,000 
135,919 

53,372 
88,559 

$695 

134,561 
31,260 

12,500 

29,108 
130,315 

1,700 
4,625 

5,751 
35,575 

107,978 
36,478 

7,500 
4,275 

34,000 
394,973 

7,500 

455',366 

462,580 

'  66,144 

827,144 

998,671 

24,666' 

537,944 

'122,666' 

Total.... 

1,588,248 

571,526 

170,562 

1,293,019 

1,184,672 

24,695 

1,557,783 

158,400 

A 

6,548,905 

a  Includes  Kentucky,  Maryland,  North 

Carolina,  and  West  Virginia. 
b  Includes  Washington. 
c  Included  in  New  Mexico. 
d  Includes  Oregon  and  Utah. 


e  Included  in  Alabama. 
/  Includes  Arizona  and  Texas. 
g  Included  in  Colorado 
h  Included  in  Alaska. 


The  following  table  shows  the  various  uses  to  which  the  marble 
quarried  in  1904,  1905,  1906,  1907,  1908,  and  1909  was  put: 

TABLE  92.  — DISTRIBUTION  AND  VALUE  OF  OUTPUT  OF 
MARBLE,  1904-1909,  AMONG  VARIOUS  USES. 


Use. 

1904. 

1905. 

1906. 

1907. 

1908. 

1909. 

Sold  by  producers  in  rough  state 
Dressed  for  building  

$2,599,052 
988,671 

$2,987,542 
1,168,450 

$1,795,169 
1,559,925 

$1,697,891 
1,905,145 

$1,455,980 
2,329  438 

$2,330,336 
1  293  019 

Ornamental  purposes 

21,554 

13,643 

44,523 

25050 

25  506 

24  695 

Dressed  for  monumental  work.  . 
Interior  decoration  in  buildings.  . 
Other  uses    .  . 

1,211,389 
1,257,963 
219,206 

1,170,279 
1,682,651 
106  506 

2,214,872 
1,722,445 
246004 

2,044,000 
1,900,952 
264  647 

1,843,426 
1,943,750 
135  820 

1,184,672 
1,557,783 
158  400 

Total  

6,297,835 

7,129,071 

7,582,938 

7  837  685 

7  733  920 

6  548  505 

Reference  List  on  Crystalline  Marbles.  —  The  following  list 
contains  the  principal  publications  dealing  with  the  subject  of 


176  BUILDING  STONES  AND  CLAYS 

marbles  in  general,   and  with  the  crystalline  marbles  in  par- 
ticular. 

General  treatise: 

Buraham,  S.  M.     The  history  and  uses  of  limestones  and  marbles,  392  pp. 

Boston,  1882. 
Alabama: 

Byrne,  P.     Marble  formations  of  the  Cahaba  River,  Alabama.     Eng.  & 

Min.  Jour.,  vol.  72,  p.  400.     1901. 
Arizona: 

Paige,  Sydney.     Marble  prospects  in  the  Chiricahua  Mountains,  Arizona. 

Bull.  380,  U.  S.  Geol.  Sur.,  pp.  299-311.     1909. 
California: 

Jackson,  A.  W.     Building  stones  (of  California).     7th  Ann.  Rep.  Cal. 

State  Min.,  pp.  206-217.     1888. 
Anon.     Marbles  of  California.     Bull.  38,  Cal.  State  Min.  Bureau,  pp. 

95-114.     1906. 
Colorado: 

Lakes,  A.     Building  and  monumental  stones  of  Colorado.     Mines  and 

Minerals,  vol.  22,  pp.  29,  30.     1901. 
Connecticut: 

Ries,  H.     The  limestone  quarries  of  eastern  New  York,  western  Vermont, 
Massachusetts,  and  Connecticut.     17th  Ann.  Rep.  U.  S.  Geol.  Sur., 
pt.  3,  pp.  795-811.     1896. 
Georgia: 

McCallie,  S.  W.     A  preliminary  report  on  the  marbles  of  Georgia.     Bull.  1, 

Ga.  Geol.  Sur.,  92  pp.     1894. 
Maryland: 

Matthews,  E.  B.     An  account  of  the  character  and  distribution  of  Mary- 
land building  stones.     Reports  Md.  Geol.  Sur.,  vol.  2,  pp.  125-241. 
1898. 
Massachusetts: 

Ries,  H.     The  limestone  quarries  of  eastern  New  York,  western  Vermont, 
Massachusetts,  and  Connecticut.     17th  Ann.  Rep.  U.  S.  Geol.  Sur., 
pt.  3,  pp.  795-811.     1896. 
Whittle,  C.  L.     The  building  and  road  stones  of  Massachusetts.     Eng. 

and  Min.  Jour.,  vol.  66,  pp.  236,  237.     1898. 
Nevada: 

Darton,  N.  H.     Marble  of  White  Pine  County,  Nevada.     Bull.  340, 

U.  S.  Geol.  Sur.,  pp.  377-380.     1908. 
New  York: 

Brinsmade,  R.  B.     Marble  quarrying  of  Gouverneur,  N.  Y.     Eng.  and 

Min.  Jour.,  Oct.  21,  1905,  pp.  728-730. 
Eckel,  E.  C.     The  quarry  industry  in  southeastern  New  York.     20th 

Ann.  Rep.  N.  Y.  State  Museum,  pp.  141-176.     1902. 
Vermont: 

Perkins,  G.  H.     Report  on  the  marble,  slate,  and  granite  industries  of 
Vermont.     68  pages,  Rutland.     1898. 


MARBLES  177 

Perkins,  G.  H.     Marble  (in  Vermont).     Rep.  Vt.  Geol.  for  1899-1900, 

pp.  38-57.     1900. 
Perkins,  G.  H.     Marble  (in  Vermont).     Rep.  Vt.  Geol.  for  1901-1902, 

pp.  40-44.     1902. 
Washington: 

Shedd,  S.     Marble  and  serpentine  deposits  of  Washington.     Ann.  Rep. 

for  1902,  Wash.  Geol.  Sur.,  pp.  75-133.     1903. 


II.  FOSSILIFEROUS   OR  SUB  CRYSTALLINE  MARBLES. 


Under  this  heading  are  included  limestones  which,  though  not 
highly  crystalline,  possess  sufficiently  close  texture  to  take  a 
good  polish,  and  at  the  same  time  show  attractive  color  effects. 
The  well-known  Tennessee  marbles  are  the  best  examples  of  this 
type  of  stone. 

Origin  and  Character.  —  Since  the  fossiliferous  or  subcrystal- 
line  marbles  are  simply  ordinary  limestones,  so  far  as  origin  is 
concerned,  nothing  can  be  added  here  to  the  discussion  of  the 
origin  of  limestones  which  has  been  presented  in  Chapter  IX. 
The  only  points  of  difference  which  require  further  consideration 
are  those  connected  with  the  color  and  texture  of  the  subcrystal- 
line  marbles. 

So  far  as  texture  is  concerned,  the  stone  is  necessarily  close- 
grained,  free  from  chert  or  clayey  matter,  and  susceptible  to  at 
least  a  fair  polish.  Distinct  calcite  crystals  are  not  visible,  but 
the  groundmass  of  the  stone  is  crystalline  and  not  earthy  in 
texture. 

In  order  to  be  salable,  the  subcrystalline  marbles  must  be 
either  of  a  particularly  attractive  or  desirable  solid  color,  or  they 
must  show  attractive  contrasting  colors.  The  first  type  is  rare, 
the  only  color  in  which  the  subcrystalline  marbles  can  excel  the 
crystalline  marbles  being  black.  The  second  type,  in  which 
contrasting  colors  are  present,  is  well-exemplified  by  the  Ten- 
nessee marbles.  In  this  second  type  much  of  the  color  effect 
is  often  due  to  the  fact  that  the  ground-mass  of  the  stone  is  of  a 
different  color  from  the  shells  or  other  fossils  which  it  contains. 

Chemical  Composition.  —  In  chemical  composition  the  sub- 
crystalline  marbles  can  of  course  show  little  of  special  interest. 
Since  the  presence  of  much  silica  or  clayey  matter  would  com- 
monly interfere  with  polishing,  the  fossiliferous  marbles  which 
reach  the  market  are  usually  fairly  pure  carbonate  rocks. 


178 


BUILDING  STONES  AND  CLAYS 


The  following  analyses  of  subcrystalline  marbles  will  serve  to 
give  some  idea  of  their  range  in  chemical  composition. 

TABLE   93. —  ANALYSES  OF  AMERICAN  SUBCRYSTALLINE 

MARBLES. 


i 

2 

3 

4 

5 

6 

7 

Silica  

0.76 
0.42 

54.67 
1.01 
43.49 

1.43 
3.28 

52.77 
0.82 
41.85 

4.23 
0.91 

30.42 
19.86 
n.d. 

0.17 
J  0.04 
10.23 
55.47 
0.30 
43.63 
0.21 

0.13 
tr. 
0.26 
55.32 
0.21 
43.51 
0.13 

0.07 

0^21 
55.12 
0.51 
43.98 

0.23 
0.16 
0.08 
55.87 
0.15 
43.47 

Alumina      J 

Iron  oxide  J 
Lime 

Magnesia     

Carbon  dioxide  
Water 

1.  Gray  marble,  Varnell  station,  Whitfield  County,  Georgia;  W.  H.  Emer- 

son, analyst;  Bull.  1,  Georgia  Geol.  Sur.,  p.  87. 

2.  Brown  marble,  Red  Clay  P.  O.,  Whitfield  County,  Georgia;  W.  H.  Emer- 

son, analyst;  Bull.  1,  Georgia  Geol.  Sur.,  p.  87. 

3.  Black  marble,  Six  Mile  Station,  Floyd  County,  Georgia;  W.  H.  Emerson, 

analyst;  Bull.  1,  Georgia  Geol.  Sur.,  p.  87. 

4.  Marble,  near  Knoxville,  Term.;  L.  G.  Eakins,  analyst;  Bull.  168,  U.  S. 

Geol.  Sur.,  p.  258. 

5.  Marble,  Hawkins  County,  Tenn.;  A.  L.  Colby,  analyst;  18th  Ann.  Rep. 

U.  S.  Geol.  Sur.,  pt.  5,  p.  983. 

6.  Marble,  near  Knoxville,  Tenn.;  Agric.  Exp.  Station,  analysts;  Bull. 

2D,  Tenn.  Geol.  Sur.,  p.  22. 

7.  Marble  from  Meadows  quarry,  Blount  County,  Tenn.;  G.  S.  Jamieson, 

analyst;  Bull.  2D,  Tenn.  Geol.  Sur.,  p.  22. 

Geological  Distribution.  —  Geological  age  is  of  interest  in  the 
present  connection  only  from  the  fact  that  the  geological  history 
of  any  limestone  must  necessarily  have  had  some  effect  upon  its 
texture  and  structure.  Subcrystalline  marbles  may  be  found 
in  limestone  formations  of  almost  any  geological  period,  but  owing 
to  the  fact  just  stated  certain  formations  are  more  likely  to  yield 
them  than  others. 

In  the  eastern  and  central  United  States,  for  example,  the 
Cambrian  and  Silurian  rocks  were  involved  in  the  earth  move- 
ments which  gave  rise  originally  to  the  mountain  ranges  which 
parallel  our  Atlantic  coast.  The  later  rocks  — Devonian  and  Car- 
boniferous—  were  rarely  involved  in  the  folding  and  metamor- 
phism  which  accompanied  these  movements.  In  consequence, 
the  areas  of  Cambrian,  Ordovician,  and  Silurian  limestones 
which  border  the  Adirondack  and  Appalachian  ranges  are  apt  to 


MARBLES  179 

show  a  certain  degree  of  metamorphism  everywhere.  Where  the 
metamorphic  effects  were  intense,  highly  crystalline  marbles  were 
developed,  as  noted  on  preceding  pages.  But  even  where  the 
metamorphism  did  not  go  to  the  extreme  of  causing  entire 
recrystallization  of  the  limestones,  there  is  an  evident  increase 
in  their  density  and  compactness  as  compared,  for  example, 
with  entirely  unaltered  Carboniferous  limestones. 

Geographic  Distribution.  —  The  earliest  worked  subcrystalline 
marbles  in  the  United  States  were  those  at  Hudson,  Glens  Falls, 
and  Lockport,  New  York.  These  were  all  of  different  type  and 
age,  the  Glens  Falls  stone  being  a  bed  in  the  Trenton  formation, 
the  Lockport  stone  coming  from  the  Niagara  group,  while  the 
Hudson  marble  was  found  in  the  Lower  Helderberg  group.  All 
three  of  the  groups  named  are  Silurian  in  age,  in  the  broader 
sense  in  which  the  term  Silurian  was  long  used. 

The  Tennessee  marbles,  which  are  by  far  the  best  known  and 
most  important  American  examples  of  the  subcrystalline  type, 
occur  as  beds  in  the  Chickamauga  formation.  This  is  of  Ordo- 
vician  age,  and  corresponds  approximately  to  the  Trenton  for- 
mation of  New  York,  which  once  furnished  similar  marbles  at 
Glens  Falls  and  elsewhere.  These  marble  beds  of  the  Chicka- 
mauga formation  occur  not  only  in  eastern  Tennessee  but  in  the 
adjoining  portions  of  Virginia  and  Georgia.  In  these  latter 
states,  however,  they  have  never  been  extensively  developed. 

Production  of  Subcrystalline  Marble.  Owing  to  the  develop- 
ment of  these  deposits  of  subcrystalline  marble,  Tennessee  ranks 
at  present  third  among  the  marble  producing  states,  being  sur- 
passed in  value  of  annual  output  only  by  Vermont  and  Georgia. 
Since  all  the  marble  output  of  Tennessee  is  of  the  subcrystalline 
type,  and  since  the  relatively  unimportant  amounts  of  subcrys- 
talline marble  produced  in  other  states  cannot  be  accurately 
determined,  the  data  as  to  production  given  below  will  be  confined 
to  the  output  of  Tennessee. 

TABLE  94.  — ANNUAL  PRODUCTION  OF  SUBCRYSTALLINE 
MARBLE,   1905-1909. 

1905 $582,229 

1906 635,821 

1907 688,148 

1908. . . : 790,233 

1909 613,741 


180 


BUILDING  STONES  AND   CLAYS 


In  the  years  noted  the  production  of  subcrystalline  marble  in 
the  United  States,  as  indicated  by  the  production  of  Tennessee, 
ranged  between  eight  per  cent  and  ten  per  cent  of  the  total  output 
of  all  kinds  of  marble  in  the  United  States. 

The  distribution  of  the  total  Tennessee  output  by  uses,  for 
the  years  1908  jand  1909,  was  as  follows: 


Use. 

1908. 

1909. 

Sold  rough,  for 
Building  stone  ....       

$83,764 

$130  315 

Monumental  stone  

10,755 

4  625 

Other  purposes  

37,575 

35,575 

Sold  dressed,  for 
Building  stone 

78  440 

36  478 

Monumental 

17  590 

4  275 

Interior  decoration 

551  449 

394  973 

Other  purposes 

10  660 

7  500 

Total  Tennessee  output  

$790,233 

$613,741 

Reference  List  on  Fossiliferous  Marbles.  —  The  following 
brief  list  includes  the  titles  of  the  more  important  publications 
referring  to  the  Tennessee  marbles,  which  are  the  only  exten- 
sively developed  fossiliferous  marbles  in  the  United  States.  The 
report  by  Gordon  is  by  far  the  most  detailed  and  important  one 
in  the  list. 

Cotton,  H.  E.,  and  Gattinger,  A.     Tennessee  building  stones.     Vol.  10, 

Reports  10th  U.  S.  Census,  pp.  187,  188.     1884. 
Gordon,  C.  B.     The  marbles  of  Tennessee.     Bull.  2D,  Tenn.  Geol.  Sur., 

33  pp.     1911. 
Keith,  A.     Tennessee  marbles.     Bull.  213,  U.  S.  Geol.  Sur.,  pp.  366-370. 

1903. 
Willis,    B.     The   marbles  of  Hawkins  County,    Tennessee.     School   of 

Mines  Quarterly,  vol.  9,  pp.  112-123.     1888. 

ONYX  MARBLES. 

Origin  and  Character.  —  The  onyx  marbles  are  deposits  of 
relatively  pure  calcium  carbonate,  deposited  by  waters  which 
have  carried  it  in  solution.  The  deposition  may  take  place  at 
the  surface,  around  the  exits  of  springs,  or  in  caves  along  the 
course  of  flow  of  underground  waters. 

During  the  course  of  this  deposition,  which  is  usually  a  slow 
and  not  necessarily  continuous  process,  changes  may  take  place 


MARBLES  181 

in  the  composition  of  the  dissolved  material  contained  in  the 
water;  and  very  slight  differences  in  the  amounts  of  iron  oxide, 
organic  matter,  or  other  coloring  material  which  is  precipitated 
along  with  the  calcium  carbonate  will  be  sufficient  to  produce 
the  color  banding  which  is  so  characteristic  and  desirable  a 
feature  of  the  onyx  marbles. 

Uses  and  Production.  —  The  onyx  marbles  are  of  practically 
no  structural  value,  and  are  used  entirely  for  decorative  purposes. 
They  are  to  be  compared,  therefore,  with  serpentine  and  some 
of  the  more  purely  decorative  crystalline  marbles. 

No  data  are  available  to  determine,  even  approximately,  the 
output  of  onyx  marbles  and  allied  products  in  the  United  States. 
In  the  statistical  reports  of  the  United  States  Geological  Survey, 
such  output,  whatever  it  may  amount  to,  is  included  in  the 
production  of  marble  and  limestone. 

It  is  known  that  onyx  marbles  are  produced  commercially  in 
California,  Arizona,  New  Mexico,  and  Utah.  In  the  states  of 
Kentucky,  Tennessee,  Virginia,  and  West  Virginia  some  attention 
has  been  paid  to  the  quarrying  or  mining  of  the  cave  marbles, 
but  no  steady  commercial  production  seems  to  have  resulted 
as  yet  in  any  of  these  states. 

Reference  List  on  Onyx  Marbles.  —  The  publications  noted  in 
the  following  brief  list  are  of  interest  as  referring  to  the  onyx 
marbles.  Of  those  listed,  Merrill's  report  of  1894  is  by  far  the 
most  important  and  complete. 

De  Kalb,  C.     Onyx  marbles.     Trans.  Am.  Inst.  Min.  Eng.,  vol.  25, 

pp.  557-569.     1896. 
De  Kalb,  C.     Onyx  marbles.     20th  Ann.  Rep.  U.  S.  Geol.  Sur.,  pt.  6, 

pp.  286-291.     1899. 
Gorby,  S.  S.     The  onyx  deposits  of  Barren  County,  Kentucky.     Eng.  & 

Min.  Jour.,  vol.  67,  pp.  707,  708.     1899. 
Merrill,  G.  P.    The  onyx  marbles;  their  origin,  composition,  and  uses, 

both  ancient  and  modern.     Rep.  U.  S.  National  Museum  for  1893, 

pp.  539-585.     1894. 

Merrill,  G.  P.     A  consideration  of  some  little-known  American  ornamen- 
tal stones.    Stone,  vol.  19,  pp.  225-230.     1899. 
Anon.     Onyx  marbles  of  California.     Bull.  38,  Cal.  State  Min.  Bureau, 

pp.  111-114.     1906. 


CHAPTER  XL 

FIELD  EXAMINATION  AND  VALUATION  OF  STONE 
PROPERTIES. 

THE  valuation  of  a  stone  property  will  usually  necessitate  a 
careful  field  examination,  some  far  less  important  laboratory 
work,  and  finally  a  study  of  the  commercial  conditions  which 
affect  values.  As  a  matter  of  fact,  the  last  of  these  is  by  far  the 
most  important,  though  it  is  rarely  even  referred  to  in  books  on 
building  stones. 

In  the  present  chapter  the  field  examination  of  stone  properties 
will  be  taken  up,  followed  by  some  consideration  of  business  con- 
ditions in  the  stone  industry.  Laboratory  tests  will  be  treated 
in  a  later  chapter. 

THE  FIELD   EXAMINATION   OF   STONE  PROPERTIES. 

Scope  of  Reports.  —  Reports  upon  stone  properties  or  quarries 
naturally  fall  into  two  quite  distinct  classes,  with  different  aims 
and  requirements.  One  class  would  include  the  detailed  expert 
examination  of  the  property  as  a  commercial  proposition,  looking 
toward  placing  the  stone  on  the  regular  market.  The  other  class 
would  include  the  much  less  detailed  report  necessary  when  stone 
from  a  certain  property  or  quarry  is  offered  for  an  important 
engineering  work.  In  this  latter  case  the  question  before  the 
engineer  is  simply  whether  or  not  the  quarry  can  reasonably  be 
expected  to  supply  a  sufficient  quantity  of  stone,  of  quality  satis- 
factory for  the  proposed  work.  In  the  former  case,  where  the 
expert  report  will  probably  be  used  as  a  basis  for  exploiting  the 
property,  many  other  features  of  the  proposition  will  require 
careful  examination;  and  a  complete  report  of  this  class  should 
include  sufficient  data  to  answer  the  following  questions: 

(1)  Is  the  stone  of  such  character  that  it  can  find  a  market 
when  placed  in  competition  with  stone  from  existing  quarries? 

(2)  Is  there  sufficient  quantity  of  good  stone  to  justify  the 
investment  necessary  for  lands  and  plant? 

182 


FIELD  EXAMINATION  OF  STONE  PROPERTIES          183 

(3)  Can  the  stone  be  quarried  and  transported  cheaply  enough 
to  compete  with  existing  quarries? 

The  property  to  be  examined  may  be  a  quarry,  either  working 
or  abandoned,  or  it  may  consist  entirely  of  undeveloped  land. 
In  the  first  case  there  will  be  little  difficulty  in  seeing  enough  of 
the  stone  to  form  a  good  idea  of  its  character,  extent,  etc.,  and 
actual  exploratory  work  will  usually  be  unnecessary.  Occa- 
sionally, however,  drilling  or  trenching  will  be  required,  even 
when  a  quarry  has  been  opened  on  the  land,  before  a  safe  estimate 
can  be  made  as  to  the  quantity  of  stone  available.  When  the 
land  is  entirely  undeveloped,  the  case  becomes  more  serious. 
Road  cuts,  railroad  cuts,  and  stream  banks  must  then  be  carefully 
examined;  and  hillsides  will  often  furnish  fairly  good  natural 
outcrops.  In  some  cases  this  will  be  sufficient,  but  if  the  pro- 
posed investment  is  heavy  it  will  be  best  to  drill  or  trench.  The 
choice  between  these  two  methods  of  examination  will  depend 
largely  on  the  kind  and  structure  of  the  rock.  In  limestones  or 
sandstones  dipping  at  a  high  angle,  trenching  across  the  strike 
of  the  beds  will  be  least  expensive,  and  more  satisfactory  than 
drilling.  For  granites  also,  which  show  no  bedding,  trenching 
is  best.  But  if  the  rocks  are  limestones  or  sandstones  lying  hori- 
zontally, or  nearly  so,  drilling  will  usually  be  more  satisfactory 
than  trenching;  and  for  roofing  slates  this  method  is  always  to 
be  preferred.  A  small  face  can  also  be  opened  up  at  the  point 
which  seems  best  suited  for  the  site  of  the  proposed  quarry,  and 
information  as  to  the  actual  working  properties  of  the  stone  can 
thus  be  obtained. 

Exploration  required.  In  nine  cases  out  of  ten,  however,  the 
engineer  called  to  report  on  a  stone  property  will  find  that  little 
exploratory  work  is  required.  Building  stone  is  so  common  a 
product  that  a  land  owner  rarely  becomes  enthusiastic  enough 
about  it  to  ask  for  an  expert  opinion  unless  the  rock  has  been 
quarried  on  his  own  or  a  neighboring  property,  or  else  shows 
naturally  in  some  particularly  imposing  cliff. 

In  examining  a  stone  property,  there  are  practically  only  two 
cases  in  which  it  will  be  advisable  to  go  to  the  expense  of  using 
the  diamond  drill.  These  are:  (1)  in  a  slate  deposit,  and  (2)  in 
a  marble  bed  dipping  at  a  high  angle  —  45  degrees  or  more.  In 
both  these  cases  the  actual  quarries  are  apt  to  take  the  form  of 
deep  narrow  cuts,  and  for  this  reason  it  will  pay  to  determine  the 


184  BUILDING  STONES  AND   CLAYS 

character  of  the  rock  to  some  depth.  But  in  all  other  cases  a 
core  drill  will  give  little  information  of  value.  Stone  can  rarely 
be  profitably  worked  by  mining,  so  that  a  drill  core  showing 
that  a  good  bed  of  stone  occurs  at  some  considerable  depth  is 
hardly  of  much  service.  In  a  granite  quarry  of  such  limited 
areal  extent  that  deep  workings  seem  probable,  it  may  pay  to 
take  out  a  few  40-  or  50-foot  cores  in  order  to  be  sure  that 
the  color  and  texture  of  the  stone  will  continue  to  be  satisfactory, 
but  in  most  cases  drilling  a  stone  prospect  is  unnecessary  and 
unadvisable. 

The  case  is,  of  course,  very  different  when  the  stone  is  to  be 
used  for  some  purpose  in  which  its  exact  chemical  composition 
is  of  importance.  If  a  sandstone  is  to  be  used  for  glass,  or  a 
limestone  for  cement,  core  drilling  is  practically  the  only  means 
of  securing  good  samples  for  analysis  of  all  the  beds  of  the  rock. 
But  this  is  a  case  which  hardly  enters  into  the  field  of  the  present 
volume. 

Schedule  for  Notes.  The  following  form  was  devised  for  use  on 
the  United  States  Geological  Survey,  as  a  general  guide  for  secur- 
ing the  proper  kind  and  amount  of  data  regarding  developed  stone 
properties.  Though  this  form  was  planned  for  a  special  purpose, 
it  will  serve  as  a  useful  framework  on  which  to  hang  brief  notes  on 
the  principal  points  to  be  observed  in  examining  either  a  quarry 
or  an  entirely  undeveloped  property.  It  will  be  seen  that  many 
of  these  points  can  be  disregarded  if  the  report  is  to  be  merely  on 
the  question  of  whether  or  not  the  property  can  supply  enough 
good  stone  for  a  given  engineering  work.  But  for  a  complete 
report,  to  be  used  as  a  basis  for  valuing  or  financing  the  property, 
all  these  points  must  be  considered.  A  few  of  the  questions,  of 
course,  can  apply  only  to  a  working  quarry. 

SCHEDULE  FOR   QUARRIES. 

1.  Name  and  address  of  owner 

2.  Name  and  address  of  lessee,  if  any 

3.  Location  of  quarry 

4.  Area  of  quarry,  maximum  and  average  depths 

5.  Amount  and  character  of  stripping 

6.  Drainage  conditions 

7.  Machinery,  hoists,  compressors,  drills,  channelers,  steam  shovels,  pumps . . 

8.  Methods  of  hoisting 

9.  Methods  of  transportation 

10.  Number  of  men  and  teams  worked 

11.  Kind  of  rock  quarried 


FIELD  EXAMINATION   OF  STONE  PROPERTIES         185 

12.  Geologic  age 

13.  Strike  and  dip 

14.  Thickness  of  beds  (for  sediments) 

15.  Distribution  and  spacing  of  joints  (for  granites,  etc.) 

16.  Segregations,  dikes,  cleavage  (for  slates),  etc.  (for  granites) 

17.  Color,  texture,  and  composition  of  rock 

18.  Visible  impurities 

19.  Discoloration  or  weathering  on  natural  exposed  surface 

20.  Chemical  composition:  name  and  address  of  analyst 

21.  Uses,     (a)   for  limestone ;  dimension  stone,  rough  stone,  road  metal,  railway 

ballast,  lime,  flux,  carbonic  acid,  pottery,  natural  cement, 

Portland  cement 

(6)  for  sandstone ;  building  stone,  grindstones,  paving,  and  flagging, 

glass  sand 

(c)  for  granites,  etc. ;  dressed  building  stone,  monumental,  rough 

stone,  paving,  etc 

22.  Annual  production 

23.  Sales  prices  per  cubic  foot  or  other  customary  measure 

24.  Total  amount  invested 

25.  Date  of  opening  quarry 

26.  Principal  market  points 

27.  Principal  buildings  or  works  supplied 


Grain.  —  Among  the  principal  points  to  be  noted  are  size  and 
regularity  of  grain  particularly  in  granites  and  sandstones. 

It  should,  however,  be  borne  in  mind  that  the  terms  "  fine- 
grained "  and  "  coarse-grained,"  as  applied  to  building  stones, 
are  entirely  comparative,  and  depend  largely  on  the  kind  of  rock 
under  consideration.  A  granite,  for  example,  whose  constituent 
minerals  averaged  J  inch  in  diameter  would  be  a  rather  fine- 
grained rock,  for  a  granite.  But  a  sandstone  whose  grains  were 
of  that  size  would  properly  be  called  a  very  coarse-grained  stone ; 
and  in  a  limestone  or  marble  grains  of  this  diameter  would  be 
exceptionally  large. 

It  would  be  better,  though  a  little  more  troublesome,  to  discard 
such  vague  comparative  terms  when  describing  a  building  stone, 
and  to  state  the  approximate  average  diameter  of  its  constituent 
particles  in  fractions  of  an  inch. 

In  addition  to  the  average  size  of  grain,  variations  in  size  are 
to  be  noted.  In  most  building  stones  the  grains,  in  any  given 
slab,  will  be  of  about  the  same  size.  But  in  some  igneous  rocks 
—  as  the  porphyries,  for  example  —  the  mass  of  the  rock  will 
consist  of  a  very  fine-grained  groundmass,  scattered  through 
which  are  large  crystals,  usually  of  the  least  fusible  constituent. 
In  sandstone,  also,  a  similar  irregularity  of  grain  is  often  observ- 
able, while  in  the  limestones,  marbles,  and  slates  such  variations 
in  size  of  grain  are  exceptional. 


186  BUILDING   STONES  AND   CLAYS 

Color.  —  In  regard  to  color,  the  points  to  be  considered  are  its 
tint,  its  permanence,  and  its  regularity,  as  all  three  are  matters 
of  commercial  importance. 

The  tint  of  the  stone  will,  of  course,  be  obvious  enough  when 
a  fresh  surface  is  examined.  In  describing  it,  comparisons  may 
be  made  with  that  of  well-known  stones  already  on  the  market, 
for  such  comparisons  will  often  convey  a  clearer  idea  than  any 
simple  statement. 

The  color  of  an  absolutely  freshly  broken  face  of  the  stone 
should  be  compared  with  that  shown  by  a  natural  weathered 
surface  in  order  to  determine  the  probable  permanence  of  the 
tint.  If  the  stone  has  been  quarried  and  used  at  some  known 
date  in  the  past,  search  should  be  made  for  old  buildings  or  old 
blocks  in  the  quarry,  as  these  will  give  a  definite  idea  as  to  the 
color  changes  which  are  likely  to  occur  in  a  given  tint. 

In  sedimentary  rocks,  different  colors  will  probably  be  shown 
by  different  beds,  but  in  any  given  bed  the  color  should  be  prac- 
tically uniform  throughout.  Any  differences  which  exist  between 
the  color  of  different  beds,  or  of  different  parts  of  the  same  bed, 
should  be  noted.  In  granites  and  allied  igneous  rocks,  it  is  often 
observed  that  irregular  blotches  occur  at  intervals,  destroying 
the  uniformity  of  the  color.  In  all  these  cases,  an  estimate 
should  be  made  of  the  ease  or  difficulty  of  supplying  a  large 
amount  of  stone  of  some  particular  tint;  for  most  contracts  for 
buildings  will  contain  some  requirement  in  this  line. 

Joints.  —  The  jointing  of  the  rock  is  one  of  the  principal 
features  to  be  noted,  for  usually  it  determines  the  size  and  shape 
of  the  largest  blocks  that  can  be  quarried.  Most  igneous  rocks, 
and  many  sedimentary  deposits,  will  show  three  intersecting 
systems  of  joint  planes,  though  they  may  be  only  apparent  on 
a  very  close  examination.  Frequently  one  of  these  systems  is 
nearly  horizontal,  and  the  other  two  close  to  vertical.  The 
horizontal  joint  plane,  if  present,  requires  no  special  description, 
but  for  planes  vertical  or  even  slightly  inclined  to  the  horizon 
the  direction  and  amount  of  dip  of  each  system  should  be  re- 
corded. This  done,  the  regularity  and  amount  of  the  spacing 
between  the  successive  joints  of  each  system  is  to  be  noted,  and 
finally  the  comparative  importance  of  the  various  systems  is 
considered. 

The  following  example  gives  a  typical  case  of  a  description 


FIELD  EXAMINATION  OF  STONE  PROPERTIES 


187 


covering  the  points  just  noted:  "  The  granite  is  cut  by  three 
series  of  joints.  The  first  series  is  by  far  the  strongest,  and  is 
practically  horizontal,  its  planes  being  spaced  from  3  to  6  feet 
apart.  The  second  series  in  order  of  importance  is  almost  ver- 
tical, striking  N.  30°  E.  and  dipping  80°  N.  W.;  with  the  spacing 
varying  from  6  to  15  feet,  the  former  being  nearer  the  average. 
The  third  series  is  comparatively  weak,  showing  only  in  certain 
parts  of  the  quarry,  its  planes  strike  N.  45°  W.,  and  dip  72°  N.  E., 
while  its  spacing,  where  the  planes  are  visible,  is  from  6  to 
10  feet  apart." 

Impurities.  —  The^presence  of  iron  pyrite,  nodules  or  bands  of 
chert,  iron  stains,  pockets  of  clay,  etc.,  is  to  be  looked  for  with 
care.  This  is  particularly  important  when  the  stone  under  con- 
sideration is  a  marble,  a  limestone,  or  a  slate. 


Fig.  22.  —  Concentric  weathering  of  granite.    (Photo  by  J.  E.  Taff.) 

Segregations  and  Dikes.  —  Granite  outcrops  or  quarry  faces 
frequently  show  lenticular  or  irregular  segregations  of  the  dark- 
colored  mineral  constituents  of  the  rock.  Similar  concentrations 


188 


BUILDING  STONES  AND  CLAYS 


of  coarse-grained  feldspar  and  quartz  also  occur.  Often  the 
outcrop  or  quarry  is  crossed  by  a  dike  or  band  of  some  other 
igneous  rock. 

Weathering.  —  The  examination  of  old  buildings,  and  of 
natural  exposures  of  the  stone  under  test,  are  valuable  aids  to  a 
determination  of  its  probable  durability.  Field  examination 
requires,  however,  a  good  knowledge  of  the  geological  history 


Fig.  23.  —  Boulders  showing  decay  of  basic  igneous  rock.     (Photo  by 
E.  C.  Eckel.) 

of  the  area  in  which  the  quarry  occurs,  as  the  degree  to  which 
a  natural  exposure  of  the  stone  has  disintegrated  will  depend  not 
only  on  the  character  of  the  stone,  but  on  the  length  of  time  it 
has  been  exposed  to  the  weather.  Rock  areas  in  New  York 
and  New  England  are  rarely  weathered  deeply,  as  this  district 
was  swept  clean  during  the  Glacial  period,  while  rocks  of  similar 
type  and  equal  durability  in  the  Southern  States  may  be  covered 
by  from  50  to  150  feet  of  material  resulting  from  their  own 
disintegration. 


FIELD  EXAMINATION  OF   STONE   PROPERTIES          189 

VALUATION  OF  STONE  PROPERTIES. 

In  the  present  section  attention  will  be  directed  to  certain 
aspects  of  the  stone  industry  which  have  not  heretofore  been 
discussed  in  print,  but  which  are  of  great  and  increasing  interest 
to  the  engineer. 

The  Engineer's  Responsibility  for  Flotations.  —  In  the  present 
condition  of  the  stone  trade  any  one,  whether  experienced  or  not, 
is  likely  to  be  called  upon  to  examine  and  report  on  stone  prop- 
erty. If  the  matter  ended  there,  this  condition  would  affect  no 
one  except  the  owner;  and  the  present  section  would  not  need 
to  be  written,  for  the  preceding  portion  of  this  chapter  covers  the 
principal  points  which  must  be  considered  in  a  merely  technical 
examination  of  a  quarry  property.  But  there  are  indications 
that  the  stone  industry  is  now  beginning  to  develop  in  a  larger 
way,  and  there  is  the  certainty  that,  if  an  engineer's  name  has 
any  value  whatever  in  banking  or  business  circles,  his  report  will 
be  used  as  a  guarantee,  not  only  of  the  technical  soundness  of 
the  proposition,  but  also  of  its  financial  soundness.  It  is  one 
thing  to  say  that  a  stone  is  attractive  in  appearance,  that  it  is 
probably  durable,  that  it  can  be  quarried  at  reasonable  cost,  and 
that  it  exists  in  a  certain  tonnage  on  a  given  property.  It  is  quite 
another  thing  to  recommend,  even  by  implication,  the  purchase 
of  securities  issued  against  this  same  property. 

This  difference  in  attitude  should  of  course  be  obvious,  and 
there  should  be  no  difficulty  in  distinguishing  between  the  two 
cases.  But  as  a  matter  of  fact  if  an  engineer  of  any  standing 
reports  on  a  new  enterprise  it  is  almost  impossible  for  him  to 
word  his  report  so  carefully  as  not  to  have  it  accepted  as  a  guaran- 
tee, not  only  of  technical  conditions,  but  of  the  financial  security 
of  the  enterprise.  Engineers  are  not  the  only  persons  likely  to 
encounter  this  difficulty,  and  the  only  reason  for  their  greater 
care  is  that  the  public  expects  more  from  them.  By  this  time 
the  public  has  become  accustomed  to  seeing  admirals,  clergymen, 
generals,  and  senators  appear  as  sponsors  for  oil  companies, 
mining  promotions,  and  all  sorts  of  swindles  —  and  it  looks  on 
this  in  the  charitable  conviction  that  of  course  they  can  know 
nothing  about  these  businesses  and  are  simply  foolish.  With 
an  engineer,  however,  the  case  is  different,  and  the  view  taken 
is  usually  far  from  charitable. 


190 


BUILDING  STONES  AND  CLAYS 


Present  Status  of  the  Stone  Industry.  —  Unlike  most  other 
American  industries,  the  stone  trade  is  still  largely  in  the  hands 
of  individuals,  or  of  relatively  small  firms  or  corporations.  The 
data  presented  below  show  that  in  1902,  the  latest  date  for 
which  statistics  on.  this  point  were  available,  the  various  sections 
of  the  stone  trade  showed  the  following  results: 

TABLE   95. —  AVERAGE    PRODUCTION    IN    AMERICAN    STONE 

TRADE. 


Kind  of  stone. 

Total  number 
of  operators. 

Total  value  of  an- 
nual product. 

Average  annual 
product  per 
operator. 

Granite  

853 

$18,257,944 

$21,404 

Slate  

174 

5,696,051 

32,736 

Sandstone 

1211 

10  601  171 

8  754 

Limestone 

3137 

30  441  801 

9  704 

Marble 

75 

5  044  182 

67  256 

It  requires  only  cursory  examination  of  these  figures  to  prove 
that  the  average  quarry  operator,  especially  in  the  sandstone 
and  limestone  industries,  is  not  a  very  important  business  interest. 
In  view  of  the  fact  that  this  condition  is  likely  to  change,  and 
that  the  larger  companies  to  come  must  base  their  capitalization 
on  the  experience  of  the  present,  it  will  be  profitable  to  consider 
these  matters  in  somewhat  more  detail. 

Average  Costs  and  Profits.  —  The  latest  detailed  figures  rela- 
tive to  the  American  stone  industry  in  1902  are  to  be  found  in  a 
report  of  the  Twelfth  Census.  The  figures  in  the  following  table 
are  copied  from  that  volume. 

TABLE  96.  —  DATA  RELATIVE  TO  THE  AMERICAN  STONE 
INDUSTRY   IN   1902. 


Granite. 

Slate. 

Sandstone. 

Limestone. 

Marble. 

Number  of  firms  or  corporations 

853 

174 

1,211 

3,137 

75 

quarries  operated  

906 

199 

1,304 

3,246 

83 

Number  of  salaried  officials 

1,377 

437 

847 

2,231 

352 

laborers  

18,836 

5,920 

10,448 

31,547 

4,070 

Total  power  employed,  H.P. 

46,986 

25,454 

25,652 

64,500 

14,286 

Total  expense  for  salaries  
wages  

$1,227,885 
11,072,996 

$334,879 
3,177,459 

$713,579 
6,153,060 

$1,843,747 
14,750,638 

$341,021 
2,212,640 

quarry  rent,  royalties,  etc  
office  rent,  taxes,  etc  

194,892 
615,314 
2  493  065 

269,267 
176,878 
680  361 

195,968 
682,812 
1  298  190 

422,693 
1,017,388 
5,403,912 

65,385 
317,492 

825,822 

Total  costs 

$15,604,152 

$4,638,844 

$9,043,609 

$23,438,378 

$3,762,360 

Total  value  of  product  

18,257,944 

5,696,051 

10,601,171 

30,441,801 

5,044,182 

FIELD  EXAMINATION  OF  STONE  PROPERTIES 


191 


The  Census  Report  figures,  though  interesting  in  themselves, 
can  readily  be  treated  so  as  to  give  more  valuable  data  on  costs. 
Unfortunately  the  report  gives  no  hint  as  to  the  quantity  of  stone 
produced  during  the  year,  so  that  the  costs  per  cubic  foot  can- 
not be  deduced.  But  the  elements  that  make  up  the  total  cost 
in  each  industry  can  be  determined,  as  well  as  the  percentage  of 
profit.  All  these  factors  can  be  expressed  in  percentages  of  the 
total  cost. 

TABLE   97. -ELEMENTS   OF   COST   IN  STONE  QUARRYING  IN 
PERCENTAGE  OF  TOTAL  COST. 


Granite. 

Slate. 

Sand- 
stone. 

Lime- 
stone. 

Marble. 

Salaries  

Per  cent. 
7.88 

Per  cent. 
7.22 

Per  cent. 

7.89 

Per  cent. 
7  86 

Per  cent. 
9  07 

Wages  

70.97 

68.49 

68.04 

62  94 

58  81 

§uarry  rent,  royalties,  etc  

1.24 

5.81 

2.17 

1  80 

1  74 

ffice  rent,  taxes,  etc 

3  94 

3  81 

7  55 

4  34 

8  43 

Supplies  and  materials 

15  97 

14  67 

14  35 

23  06 

21  95 

Total  costs.  . 

100  00 

100  00 

100  00 

100  00 

100  00 

Value  of  product  . 

117  01 

122  8 

117  2 

129  87 

134  1 

The  Financing  of  the  Future.  —  From  the  data  given  in  pre- 
vious paragraphs  it  can  be  readily  understood  that  the  stone 
trade  of  the  present  day  is  on  a  very  different  basis  from  most 
of  the  other  large  industries.  For  the  most  part,  it  is  handled 
by  small  operators,  whether  individuals,  firms,  or  corporations. 
In  many  cases,  particularly  in  the  sandstone  and  limestone  trades, 
the  quarries  are  operated  only  at  intervals,  and  are  not  the  most 
important  business  interests  of  their  owners.  It  is,  in  the  writer's 
opinion,  highly  improbable  that  this  condition  will  last  much 
longer,  for  in  many  cases  there  are  opportunities  for  the  develop- 
ment of  the  business  on  a  larger  scale. 

If  the  stone  trade  of  the  future  is  to  be  a  more  highly  concen- 
trated industry,  it  will  require  financing  on  a  different  basis  than 
is  now  employed.  A  company  operating  a  number  of  quarries, 
in  different  localities  and  on  different  classes  of  stone,  must  put 
all  of  its  affairs  on  a  permanent  and  definite  basis.  And  it  is 
this  type  of  company,  capable  of  taking  contracts  for  any  type 
of  stone  at  any  delivery  point,  that  seems  to  offer  the  only 
possibility  for  large  profits  in  the  stone  industry. 

Characteristics  of  Industrial  Bonds.  —  Among  the  few  quarry 


192  BUILDING   STONES  AND   CLAYS 

companies  which  have  offered  their  securities  during  the  past 
few  years,  there  is  seen  the  same  tendency  toward  financing  by 
means  of  bond  issues  that  has  become  so  serious  a  feature  in 
other  industries. 

As  distinguished  from  railroad  bonds,  industrial  bonds  are 
inherently  subject  to  one  point  of  danger. 

A  railroad  line,  even  if  temporarily  unprofitable,  is  rarely 
entirely  abandoned,  for  the  growth  of  traffic  with  the  growth  of 
the  country  will  gradually  transform  it  into  a  profitable  enter- 
prise. In  addition  the  natural  increase  in  the  value  of  the  real 
estate  which  it  must  own,  and  particularly  in  the  value  of  its 
terminals,  aids  in  placing  material  assets  in  back  of  its  bonds, 
irrespective  of  the  earning  power  of  the  line  itself.  This  con- 
dition is  characteristic  of  a  growing  country,  and  can  be  expected 
to  persist  for  some  time  in  the  United  States.  When  it  finally 
ceases,  railroad  securities  will  lose  one  great  element  of  their 
strength  as  compared  with  industrials.  But  until  that  time 
comes  this  condition  must  be  reckoned  with. 

An  industrial  bond,  on  the  other  hand,  must  always  face  the 
danger  that  the  original  project  was  inherently  unsound  in  plan. 
Men  embark  in  new  industries,  or  in  old  industries  at  new  loca- 
tions, with  the  expectations  that  a  marketable  product  can  be 
made  at  a  given  point,  that  it  can  secure  a  sufficiently  large 
market,  and  that  the  prices  realized  will  be  above  the  cost  of 
manufacture  and  delivery.  If  all  of  these  expectations  are 
realized  the  operation  will  be  profitable.  But  if  any  one  of  the 
three  elements  turns  out  to  have  been  estimated  erroneously,  the 
enterprise  will  necessarily  be  unprofitable.  This  in  turn  will 
finally  mean  default  on  the  bond  interest,  for  which  the  only 
remedy  is  foreclosure  —  and  in  the  case  of  an  unsuccessful  in- 
dustrial enterprise  foreclosure  offers  little  hope  for  the  bond- 
holders. Unless  it  can  be  determined  that  the  failure  is  due, 
not  to  inherent  unsoundness  of  the  project,  but  to  mismanage- 
ment, there  is,  of  course,  no  inducement  for  anyone  to  reorganize 
the  company  and  to  put  the  plant  into  operation  again.  The 
scrapping  value  of  an  inactive  and  unsuccessful  mill  is  small, 
and  there  is  rarely  sufficient,  real  estate  to  aid  materially  in 
paying  off  the  bonds. 

Raw  Materials  as  a  Basis  for  Bond  Issues.  —  The  effect  of 
these  conditions  must  be  considered  when  an  attempt  is  made  to 


FIELD  EXAMINATION  OF  STONE  PROPERTIES          193 

place  a  value  on  bonds  issued  by  a  quarry  company.  Especial 
care  must  be  taken  when  the  bond  issue  is  so  large  that  some  or 
all  of  it  is  based,  not  on  tangible  property,  but  on  an  assumed 
value  for  the  stone  properties  held.  Each  case  must,  of  course, 
be  considered  separately,  but  'the  writer  believes  that  the  follow- 
ing rules  will  be  found  almost  universally  applicable. 

1.  Under  ordinary  competitive  conditions,  the  raw  materials 
should  not  be  credited  with  any  value  whatever  in  determining 
the  security  back  of  a  proposed  bond  issue  on  a  new  quarry 
enterprise. 

2.  If  the  stone  to  be  quarried  is  of  a  peculiarly  desirable 
quality,  and  if  the  supply  is  so  closely  controlled  as  to  possess  a 
distinct  and  measurable  monopoly  value,  this  can  be  taken  into 
the  account. 

3.  If  the  operation,  though  the  supply  of  stone  is  not  entirely 
controlled,  possesses  differential  freight  rates  to  an  important 
market  over  its  nearest  possible  competitor,  the  increased  profits 
arising  from  this  source  can  fairly  be  considered  as  an  element  in 
valuation,  and  some  portion  of  these  excess  profits  can  safely 
be  capitalized  in  the  form  of  bonds. 

Stock  Issues  against  Quarry  Projects.  —  In  the  preceding 
sections  it  has  been  pointed  out  that  bonds  issued  against  new 
quarry  projects  are  necessarily  open  to  criticism,  and  are  often, 
if  not  usually,  of  doubtful  security. 

With  regard  to  stock  issues  the  case  is  very  different.  There 
is  no  absolute  necessity  that  bonds  be  issued  at  all,  but  there  is 
the  practical  certainty  that  any  large  enterprise  will  be  put  in 
corporate  form,  and  this  implies  the  issue  of  at  least  one  class  of 
stock.  There  is,  therefore,  no  question  as  to  the  necessity  or 
propriety  of  a  stock  issue,  the  only  problem  being  the  proper  size 
of  such  issue.  The  question  here  concerns  the  practice  which 
public-spirited  Congressmen  from  agricultural  districts  hold  up 
to  public  execration  as  stock  watering. 

From  the  rigidly  conservative  point  of  view,  stock  watering 
is  the  issue  of  stock  in  such  quantity  that  the  total  par  value  of 
the  outstanding  securities  exceeds  the  amount  of  cash  actually 
invested  in  the  enterprise.  If  this  definition  were  commonly 
accepted,  it  might  truthfully  be  said  that  no  business  corpora- 
tion, in  any  country  or  at  any  time,  ever  had  absolutely  un- 
watered  stock. 


194  BUILDING  STONES  AND   CLAYS 

The  banker  or  business  man  interested  in  industrial  enter- 
prises, however,  would  modify  this  definition  materially.  To 
him,  watered  stock  is  stock  issued  in  excess  of  the  capitalized 
value  of  the  average  annual  net  profits  of  the  enterprise.  In  the 
case  of  an  established  industrial  enterprise,  this  capital  value 
might  be  estimated  by  capitalizing  the  actual  average  net  earn- 
ings, over  a  term  of  years,  after  allowing  for  depreciation  and 
other  proper  charges,  on  a  7  per  cent  basis.  In  the  case  of  an 
entirely  new  enterprise,  since  the  prospective  profits  are  certain 
to  be  estimated  too  high,  the  average  probable  earnings  could 
only  be  capitalized  on  a  much  higher  interest  basis,  say,  at  a 
10  or  15  per  cent  rate. 


CHAPTER  XII. 
LABORATORY  TESTING   OF   STONE. 

Trend  of  Testing  Methods.  —  Though  cement  and  stone  are 
closely  related  structural  materials,  the  study  and  testing  of  their 
properties  have  taken  curiously  divergent  courses. 

The  subject  of  cement  testing  has  for  many  years  been  of 
great  interest  to  both  engineers  and  cement  manufacturers,  and 
much  attention  has  been  paid  to  devising  methods  which  would 
best  bring  out  the  structural  value  of  the  material.  Through 
the  efforts  of  powerful  engineering  and  trade  societies,  both 
general  tests  and  methods  of  manipulation  have  become  fairly 
well  standardized,  and  it  is  now  possible  to  compare,  within 
certain  limits,  results  obtained  by  different  workers  and  in 
different  laboratories.  The  German  Association  of  Portland 
Cement  Manufacturers  has  done  much  in  this  direction,  while 
in  the  United  States  the  American  Society  of  Civil  Engineers 
has  taken  the  lead  in  the  standardization  of  physical  tests  of 
cement,  and  the  Society  of  Chemical  Industry  has  been  engaged 
in  securing  uniformity  in  the  methods  of  chemical  analysis. 
The  testing  of  cement,  as  compared  with  that  of  building  stone, 
has,  of  course,  the  advantage  that  information  gained  by  tests 
can  be  applied  to  the  methods  of  manufacture  so  as  to  avoid,  in 
future,  defects  which  may  have  been  detected. 

The  testing  of  structural  stone  has,  in  the  meantime,  taken 
an  entirely  different  course,  and  with  less  satisfactory  results. 
Though  earlier  contributions  to  the  study  of  the  subject  had 
been  made,  the  work  of  Gen.  Q.  A.  Gillmore  thirty  years  ago 
may  be  regarded  as  the  foundation  on  which  the  modern  study 
of  building  stone  testing  has  been  based.  The  accuracy  of  cer- 
tain of  Gillmore 's  conclusions  may  be  questioned,  but  the  real 
value  of  his  work  cannot  be  minimized.  Physical  methods  of 
testing  building  stone  have  advanced  but  slightly  since  his  day. 

Since  the  time  of  Gillmore 's  work,  however,  another  phase  of 
the  subject  has  been  studied.  The  principal  recent  investiga- 

195 


196  BUILDING  STONES  AND  CLAYS 

tions  have  been  made,  not  by  engineers,  but  by  geologists;  and 
these  have  been  concerned  with  the  durability,  rather  than  with 
the  strength  of  the  material  examined.  This  fact  has  exercised 
a  very  appreciable  influence  on  the  course  which  the  study  has 
taken.  Any  present-day  report  on  building  stones,  whether  it 
be  a  private  report  on  individual  quarries  or  a  public  report 
issued  by  Federal  or  State  geological  surveys,  will  be  found  to 
show  the  influence  of  the  classic  work  of  Hawes,  Merrill,  and 
Julien,  as  embodied  in  the  "  Report  on  Building  Stones,"  which 
forms  Vol.  10  of  the  Tenth  Census  Reports. 
T>-The  result  of  the  division  of  the  subject  between  geologists 
and  engineers  has  been  that  little  attempt  to  secure  uniformity 
of  methods  has  been  made  by- any  of  the  engineering  societies 
which  alone  are  strong  enough  to  carry  out  such  an  attempt. 
This  unsatisfactory  condition,  which  prevents  comparison  of 
the  results  obtained  in  different  laboratories,  is  due  in  large  part 
to  the  complexity  of  the  subject,  and  in  so  far  can  be  obviated 
only  by  further  work.  It  is  due  in  part,  however,  to  the  con- 
ditions under  which  previous  investigations  have  been  carried 

1  on,  and  to  better  these  united  effort  is  essential. 
/  It  would  appear  desirable  that  this  subject  be  taken  up  by 
one  or  more  of  the  American  engineering  societies,  which  alone 
possess  sufficient  influence  to  make  any  proposed  series  of  tests 
the  standard.  In  one  way,  indeed,  it  will  be  easier  to  secure 
uniformity  in  this  branch  of  investigation,  for  testing  machines 
capable  of  handling  a  stone  cube  are  much  fewer  in  number  than 
are  the  smaller  machines  used  for  testing  cements. 

Data  Required  from  Tests.  —  The  points  which  an  engineer 

'or  architect  desires  to  know  concerning  any  building  stone  are 
two  in  number: 

(1)  Is  the  stone  strong  enough  for  the  use  to  which  it  is  to  be 
put? 

(2)  Will  the  stone  retain  its  strength,  structure,  and  color 
after  exposure  for  a  long  series  of  years  to  the  natural  and  arti- 
ficial agencies  which  may  be  expected  to  attack  it? 

The  two  prime  requisites  of  a  building  stone  are,  therefore, 
strength  and  durability;  and  most  of  the  different  tests  which  will 
be  discussed  in  the  present  chapter  have  been  devised  merely 
to  determine  one  of  these  two  points,  either  directly  or  indirectly. 
This  fact  is  sometimes  lost  sight  of  by  the  experimenter  who,  in 


LABORATORY  TESTING   OF  STONE 


197 


his  zeal  for  distinction,  devises  tests  which  may  be  of  interest 
in  themselves  but  which  throw  no  light  on  the  questions  of  real 
importance. 

Classes  of  Tests  Applied.  —  As  a  matter  of  convenience,  it 
seems  advisable  to  group  the  various  possible  laboratory  tests 
according  to  the  kind  of  information  which  they  will  give  re- 
garding the  specimen  under  test.  This  has  accordingly  been 
done  in  the  following  scheme. 

I.   Tests  to  determine  composition    (  Chemical  analysis 


and  structure 
II.   Tests  to  determine  density 


III.   Tests  to  determine  durability 


IV.  Tests  to  determine  strength 


(  Microscopic  examination 
I'  Specific  gravity 
^  Weight 
^  Porosity 
f  Absorption 
I  Freezing 
«j  Sulphate  of  soda 

Resistance  to  acids 
[Heat 
'Compression 

Transverse 

Shear 

Elasticity 

Fatigue 

Hardness 

Abrasion 

Impact 


I.  TESTS  TO   DETERMINE   COMPOSITION  AND   STRUCTURE. 

Chemical  Tests.  —  In  regard  to  uniformity  in  analytical 
methods  marked  progress  has  been  made  during  the  past  few 
years.  '  Dr.  W.  F.  Hillebrand  has  described  *  in  great  detail  the 
methods  of  rock  analysis  followed  in  the  laboratory  of  the  United 
States  Geological  Survey,  and  it  seems  probable  that  future 
progress  in  the  standardization  of  such  methods  will  follow  closely 
along  the  lines  of  his  paper.  The  analysis  of  materials  for  the 
manufacture  of  Portland  cement,  a  subject  which  necessitates 
discussion  of  analyses  of  limestone,  has  been  reported  f  upon  by 
a  committee  of  the  Society  of  Chemical  Industry.  If  followed 

*  W.  F.  Hillebrand.  Some  principles  and  methods  of  rock  analysis. 
Bull.  176,  U.  S.  Geol.  Sur. 

t  Report  of  the  subcommittee  on  uniformity  in  analysis  of  materials  for 
the  Portland  cement  industry.  Jour.  Soc.  of  Chem.  Ind.,  vol.  21,  pp.  12-30. 


198  BUILDING  STONES  AND  CLAYS 


A 

V 


by  che^hists  engaged  in  industrial  work,  the  methods  advocated 
in  the  two  papers*  noted  will  result  in  greater  accuracy  in  deter- 
mining the  chemical  composition  of  rocks,  as  well  as  greater 
uniformity  in  the  statement  of  results. 

The  practical  value  of  a  chemical  analysis  depends  largely  on 
the  type  of  rock  in  question.  In  the  case  of  a  granite,  trap,  or 
other  crystalline  igneous  rock,  an  analysis  is  of  itself  of  little 
service,  though  it  may  do  some  good  if  taken  in  connection  with  a 
careful  microscopical  investigation.  With  sandstones,  analyses 
are  somewhat  more  useful,  in  determining  the  character  of  the 
cementing  material,  though  even  here  a  microscopical  investi- 
gation will  probably  be  more  serviceable.  The  value  of  a  chem- 
ical analysis  is  greater  in  the  case  of  limestones  and  slates, 
particularly  the  latter. 

Microscopic  Examination.  —  The  examination,  under  the 
microscope,  of  thin  sections  of  a  stone  serves  to  determine  the 
characters  and  condition  of  the  component  minerals,  the  shape 
and  method  of  aggregation  of  the  individual  grains;  and,  in  the 
case  of  sedimentary  rocks,  the  character  of  the  cementing  material. 
Microscopic  examination,  therefore,  is  perhaps  the  most  valuable 
single  test;  but  it  is  the  one  which  can  least  readily  be  applied  by 
the  quarryman  or  engineer,  as  instruments  and  training  are  rarely 
obtainable. 

II.   TESTS   TO   DETERMINE  DENSITY. 

Of  the  various  properties  of  stone  that  may  be  selected  for 
testing,  three  are  so  intimately  related  that  they  must  be  con- 
sidered together  under  the  head  of  tests  to  determine  density. 
The  three  properties  in  question  are: 

(1)  Specific  gravity. 

(2)  Weight  per  cubic  foot. 

(3)  Porosity. 

Of  these,  the  first  and  second  are  readily  determinable  by 
direct  experiment.  The  third  cannot  readily  or  accurately  be 
determined  by  experiment,  but  can  be  ascertained  by  calcu- 
lation when  the  weight  and  specific  gravity  are  known. 

Interrelation  of  These  Properties.  —  The  specific  gravity  of 
any  mass  of  material  is  the  ratio  between  its  density  and  that 
of  an  equal  volume  of  water.  There  is,  therefore,  a  very  simple 
relation  between  the  specific  gravity  of  any  nonporous  body 


LABORATORY  TESTING  OF  STONE  199 

and  its  weight  per  cubic  foot,  and  the  two  are  convertible  accord- 
ing to  the  following  formulas,  assuming  that  a  cubic  foot  of 
water  will  weigh  62.4  pounds. 

(1)  Specific  gravity  X  62.4  =  weight  in  pounds  per  cubic  foot. 

,-N    Weight  in  pounds  per  cubic  foot  .„  ., 

(2)  '  624  -  =  specific  gravity. 

If  we  were  dealing  with  a  thoroughly  homogeneous  and  non- 
porous  material,  such  as  rolled  steel  or  coined  gold,  the  above 
statements  would  cover  the  whole  case.  But  in  dealing  with 
stone,  which  is  rarely  homogeneous  and  usually  very  porous, 
the  matter  becomes  more  difficult,  and  any  apparently  simple, 
direct  statement  regarding  it  is  apt  to  be  misleading. 

The  difficulty  arises  from  the  fact  that  a  stone  is  made  up  of 
a  number  of  solid  nonabsorbent  mineral  particles,  separated  by 
pore  spaces  of  greater  or  lesser  size  and  amount.  We  might 
attempt  to  determine  the  specific  gravity  of  the  stone  by  simply 
weighing  a  fragment  in  air  and  then  in  water,  using  the  familiar 
formula : 

Weight  in  air 


Specific  gravity  = 


Loss  of  weight  in  water 


But  the  value  thus  obtained  would  not  be  the  true  specific 
gravity  of  the  stone.  It  would  always  be  lower  than  the  true 
specific  gravity,  because  of  the  pore  spaces  in  the  rock.  This 
fact  is  often  stated  in  discussions  of  testing  methods,  and  various 
devices  have  been  employed  to  overcome  the  difficulty.  In  the 
opinion- of  the  writer  these  attempts  have  been  wrongly  directed, 
and  have  tended  to  lessen  the  accuracy  of  the  results  rather  than 
increase  it. 

The  true  specific  gravity  of  any  stone  is  equal  to  the  specific 
gravity  of  its  solid  particles.  It  can  only  be  determined,  there- 
fore, by  grinding  the  stone  to  powder,  and  finding  the  specific 
gravity  of  this  powder.  Any  other  method  of  ascertaining  it 
will  give  erroneous  results,  the  amount  of  the  error  being  pro- 
portional to  the  porosity  of  the  original  rock. 

The  weight  per  cubic  foot  of  the  stone  can  best  be  obtained  by 
direct  weighing  of  a  carefully  measured  cube  or  slab.  The 
accuracy  of  this  direct  method  depends  on  the  precision  of  the 
measurements  and  weighing,  and  on  the  smoothness  of  the  faces 


200  BUILDING  STONES  AND  CLAYS 

of  the  cube.  A  polished  specimen,  for  example,  should  give 
very  accurate  results. 

The  porosity  of  the  stone  can  be  deduced  if  the  true  specific 
gravity  and  weight  per  cubic  foot  are  known.  The  formulas 
for  converting  these  three  factors  are  as  follows: 

g  =  true  specific  gravity  of  powder. 

w  =  apparent  weight  per  cubic  foot  by  direct  weighing. 

p  =  percentage  of  pore  space. 

-j>  =  6240  g  -  62.4  gp 

100 

(2>*  =  io°-SS- 

100  w 


(3)  g  = 


6240  -  62.4  p 


These  formulas  are  of  use,  of  course,  only  when  the  true  specific 
gravity  and  the  weight  per  cubic  foot  of  the  stone  have  been  cor- 
rectly determined.  When  the  so-called  "  specific  gravity  "  and 
"  weight  per  cubic  foot  "  have  been  determined  by  the  inaccurate 
methods  in  common  use  the  formulas  cannot  be  applied. 

Methods  of  Determining  Weight  per  Cubic  Foot.  —  The  weight 
per  cubic  foot  of  a  stone,  as  that  term  is  here  used,  is  the  actual 
weight  of  a  cubic  foot  of  the  dry  stone,  without  allowance  for 
pore  spaces. 

Two  methods  may  be  employed  in  making  this  determination. 
The  first  of  these,  though  apparently  the  cruder,  is  in  reality 
subject  to  less  error. 

(1)  Direct  Weighing.  —  A  cube  or  slab  of  the  stone  is  carefully 
measured,  and  its  volume  calculated.  It  is  then  weighed  with 
equal  care.  The  weight  per  cubic  foot  is  then,  simply,  weight 
in  pounds  per  cubic  foot  =  weight  of  specimen  in  pounds  X 

— : —    — : r^ — : — r —  •      The   specimen,    before 

volume  of  specimen  in  cubic  inches 

weighing,  should  have  been  dried  for  several  hours  at  a  tem- 
perature of  about  110°  C.  in  order  to  remove  water.  As  errors 
in  either  measuring  or  weighing  decrease  as  the  size  of  the  speci- 
men increases,  it  should  be  as  large  as  possible.  With  polished, 
well-squared  specimens  the  results  obtained  by  this  method  are 
very  accurate.  Their  accuracy  decreases,  of  course,  as  the  faces 


LABORATORY  TESTING  OF  STONE  201 

of  the  cube  or  slab  are  rougher  or  more  irregular;  but  the  cubes 
employed  for  compression  tests  will  give  very  satisfactory  re- 
sults. 

(2)  Weighing  in  Water.  —  A  method  which  some  testing  labor- 
atories use  to  determine  what  they  erroneously  call  the  "  specific 
gravity  "  of  stone,  is  in  reality  a  very  fair  method  for  obtaining 
its  weight  per  cubic  foot. 

The  specimen  is  dried  and  weighed  in  air.  It  is  then  suspended 
in  water  and  weighed  as  quickly  as  possible,  so  as  to  avoid  much 
absorption.  If  w  equals  weight  in  air,  and  w1,  weight  in  water, 
then: 

w 
Weight  in  pounds  per  cubic  foot  =  -      —  -  X  62.4. 

w  —  w1 

Porosity.  —  The  percentage  of  porosity  of  a  stone  is  the  ratio 
between  the  volume  of  pore  spaces  in  any  specimen  and  the  total 
apparent  volume  of  the  specimen.  There  is  no  simple  method 
of  determining  this  by  direct  experiment,  but  on  a  preceding 
page  it  has  been  pointed  out  that  the  porosity  can  be  calculated 
readily  if  the  true  specific  gravity  and  the  apparent  weight  per 
cubic  foot  have  been  determined.  The  formula  to  be  used  for 
this  purpose  is 

100  w 


in  which         p  =  percentage  of  pore  space. 

w  =  apparent  weight  in  pounds  per  cubic  foot. 
g  =  true  specific  gravity. 

The  value  thus  obtained  is  of  interest  simply  as  fixing  a  maxi- 
mum for  the  amount  of  water  that  can  be  absorbed  by  the  stone 
under  the  most  favorable  circumstances  possible.  Actually,  as 
below  noted,  the  absorption  rarely  approaches  this  theoretical 
maximum. 

Value  of  Density  Tests.  —  (1)  When  stone  is  to  be  used  for 
certain  purposes,  a  high  weight  per  cubic  foot  is  per  se  an  ad- 
vantage. This  is  particularly  the  case  with  regard  to  stone  to 
be  used  under  water,  as  in  dams,  breakwaters,  and  shore  pro- 
tection works.  For  such  purposes  a  trap,  weighing  perhaps 
180  pounds  per  cubic  foot,  is  a  far  more  satisfactory  material 
than  a  sandstone  weighing  only  140  pounds.  The  real  ratio 


202  BUILDING   STONES  AND  CLAYS 

between  the  value  of  these  two  stones  would  not  be  simply  that 
of  their  weights,  as  180  :  140,  but  a  much  higher  ratio.  As 
Johnson  has  pointed  out,  the  effective  weight  of  a  stone  in  under- 
water construction  is  its  weight  minus  that  of  an  equal  quantity 
of  water.  In  the  example  just  cited,  therefore,  the  real  ratio 
of  effectiveness  between  the  two  rocks  would  not  be  simply 


180-62.4      117.6 

140-62.4'  -7™  or  almost  11:  7. 

Obviously  there  is  a  distinct  advantage  to  be  gained  by  using 
stone  of  high  specific  gravity  for  such  purposes. 

(2)  Aside  from  the  case  above  mentioned,  where  high  specific 
gravity  is  of  itself  desirable,  it  is  always  desirable  because  of  the 
other  physical  properties  which  it  indicates.  It  may  be  accepted 
as  axiomatic  that  in  any  particular  group  of  stones,  the  one  show- 
ing the  highest  weight  per  cubic  foot  is  almost  certainly  the  strongest 
and  least  absorbent.  A  limestone  weighing  160  pounds  per  cubic 
foot  is,  therefore,  other  things  being  equal,  to  be  preferred  to  one 
weighing  only  140  pounds.  The  same  is  true  with  regard  to 
sandstones.  Granites  and  traps,  however,  show  such  a  small 
percentage  of  absorption  that  the  relation  between  weight  and 
absorption  becomes  of  little  practical  importance. 


m.     TESTS   TO   DETERMINE  DURABILITY. 

Expansion.  —  It  has  long  been  recognized  that  much  of  the 
lack  of  durability  of  building  stone  is  due  to  the  effects  of  changes 
of  temperature.  These  operate  to  disintegrate  the  stone  be- 
cause, except  in  the  case  of  an  entirely  homogeneous  material, 
the  various  component  minerals  will  have  different  ratios  of 
expansion  on  heating,  as  in  a  granite,  while  in  sandstones  the 
cementing  material  and  the  enclosed  grains  or  fragments  may 
expand  unequally. 

The  tendency  of  a  stone  to  exfoliate  or  disintegrate  under 
changes  of  temperature  can  obviously  be  tested  directly,  and 
uniformity  in  the  method  of  applying  the  test  may  be  obtained 
without  difficulty. 


LABORATORY  TESTING  OF  STONE  203 

Absorption.  —  The  mineral  particles  of  which  a  stone  is  com- 
posed are  themselves  practically  nonabsorbent,  but  a  certain 
amount  of  space  always  exists  between  these  particles.  This 
percentage  of  pore  space  can  be  determined  from  formula  2  on 
page  200.  Its  principal  interest  lies  in  the  fact  that  it  fixes  a 
maximum  limit  for  the  amount  of  water  that  the  stone  can 
absorb.  A  stone  containing  5  per  cent  of  pore  spaces  can  ob- 
viously never  absorb  more  water  than  would  fill  this  5  per  cent 
of  unoccupied  space.  In  reality,  under  ordinary  conditions,  it 
would  never  absorb  nearly  as  much  as  this  theoretical  maximum. 
Direct  absorption  tests  can  of  course  be  readily  carried  out;  and 
would  be  of  value  if  different  experimenters  would  accept  some 
definite  standards  of  practice  in  the  matter. 

Frost  Tests.  —  Changes  of  temperature,  as  indicated  above, 
may  of  themselves  cause  serious  injury  to  a  stone;  but  when 
taken  in  connection  with  the  action  of  water  contained  in  the 
pores  of  the  stone,  the  effect  is  greatly  augmented.  The  tests 
applied  for  expansion  are  mainly  to  determine  the  effect  of  alter- 
nate heating  and  cooling,  and  particularly  of  high  heating  and 
rapid  cooling.  The  tests  for  porosity  or  absorption,  on  the  other 
hand,  are  carried  out  with  a  view  to  determining  the  probable 
resistance  of  the  stone  to  the  action  of  frost.  Other  things  being 
equal,  it  is  obvious  that  the  stone  which  absorbs  the  greatest 
quantity  of  water  per  cubic  inch  in  a  given  time  will  be  the  stone 
that  is  subject  to  the  greatest  injury  at  low  temperature,  owing 
to  the  freezing  of  the  water  contained  in  it.  It  is  of  course  de- 
sirable to  check  up  this  mode  of  reasoning  by  carrying  out  actual 
freezing  tests;  and  several  valuable  series  of  such  tests  are  on 
record. 

The  action  of  frost  is  frequently  simulated  by  using  in  the 
absorption  test,  instead  of  pure  water,  a  saturated  solution  of 
some  salt,  of  which  expansion,  on  solidifying,  would  tend  to 
crack  or  disintegrate  the  stone.  Tests  of  this  type  have,  how- 
ever, fallen  largely  into  disuse.  They  will  be  discussed  briefly 
after  actual  freezing  tests  have  been  considered. 

In  1890  Gerber  *  tested  a  small  series  of  western  building  stones, 

the  specimens  being  subjected  to  alternate  thawing  and  freezing 

by  immersing  them  in  water  during  the  day,  and  at  night  placing 

them  in  cold  storage  rooms  kept  at  an  average  temperature  of 

*  Trans.  Am.  Soc.,  Vol.  33,  p.  253. 


204 


BUILDING  STONES  AND  CLAYS 


0°  to  4°  F.     This  was  done  for  about  twelve  days,  and  resulted 
in  the  following  losses  of  weight: 

TABLE  98.— EFFECT  OF  FREEZING  TESTS.  (GERBER.) 


Kind  of  stone. 

Location. 

Loss  of  weight  in 
per  cent. 

Limestone  

Bedford,  Ind  

0  097 

Bedford  Ind 

0   103 

Stone  City,  Iowa 

0  134 

Stone  City,  Iowa 

0  053 

Mankato,  Minn  

0  113 

Mankato,  Minn  

0  106 

Winona  Minn 

0  049 

Winona  Minn. 

0  043 

Hannibal   Mo. 

0  154 

Sandstone  

Ashland,  Wis. 

0  068 

it 

Ashland,  Wis  

0  088 

Beare  *  subjected  a  small  series  of  British  building  stones  to 
actual  freezing  tests.  The  cubes  were  soaked  in  water  all  day, 
and  then  at  night  placed  outside,  being  thus  subjected  to  tem- 
peratures of  from  20°  to  32°  F.  In  the  morning  the  specimens 
were  brought  inside  and  thawed  by  gentle  warming.  This 
process  was  repeated  ten  or  twelve  times,  and  then  the  cubes 
were  exposed  to  the  atmosphere  and  rains  for  two  or  three  weeks 
in  thawing  weather.  On  weighing  and  testing  it  was  found  that 
(1)  granite  cubes  showed  no  perceptible  loss  of  weight;  (2)  some 
limestone  and  sandstone  cubes  showed  losses,  never  exceeding 
one-fifth  of  1  per  cent;  (3)  none  of  the  cubes  showed  any  loss  of 
strength  as  compared  with  unfrozen  cubes.  Taking  into  con- 
sideration the  fact  that  most  of  the  limestones  tested  were  porous, 
loose-grained  volites,  and  that  the  group  of  sandstones  also 
included  some  very  porous  specimens,  the  small  loss  of  weight 
would  seem  to  prove  that  this  method  of  testing  could  hardly 
be  regarded  as  satisfactory. 

Buckley's  tests  on  Wisconsin  stones  gave  the  following  results : 


Proc.  Institute  Civil  Engineers,  vol.  107,  pp.  350,  351  (1892). 


LABORATORY  TESTING  OF  STONE 


205 


TABLE  99.  —  EFFECT  OF  FREEZING  TESTS.     (BUCKLEY.) 


Kind  of  stone. 

Quarry. 

Location. 

1 

*1 

P 

*o 

Compressive 
strength,  pounds  per 
square  inch. 

« 

i 

«5 

Granite 

Limestone 
Sandstone 

Amberg  Granite  Co.  . 
Berlin  Granite  Co  
Nelson  Granite  Co.  .  . 
French  Granite  Co.  .  . 
Granite  Heights  Co.  . 
Jenks'  quarry  
Leuthold  quarry  
Milwaukee  Mon.  Co.  . 
Montello  Granite  Co.. 
New  Hill  o'  Fair  
Pike    River    Granite 
Co. 

Athelstane  
Berlin 

.025 
.000 
.03 
.006 
.025 
.035 
.02 
.015 
.01 
.05 

.015 

.16 
.00 
.14 
.013 
.00 
.00 
.00 
.035 
.012 
.045 
.08 

.435 

.175 
.140 
.115 

.200 
.195 
.026 
.13 
.133 

.00 

19,988 
24,800 
45,841 
24,229 
22,507 
18,023 
25,000 
34,640 
38,244 
27,262 

23,062 

30,680 
8,098 
24,522 
35,970 
32,992 
41,620 
32,710 
8,799 
18,477 
12,827 
30,745 

4,173 

5,495 
5,421 

4,718 

5,991 
2,722 
12,405 
4,040 
5,329 

4,319 

10,619 
36,009 
32,766 
16,019 
20,306 
15,764 
14,886 
31,844 
35,045 
19,368 

20,442 

17,005 
7,527 
28,392 
20,777 
28,133 
27,366 
13,986 
9,462 
25,779 
7,554 
14,943 

2,220 

5,930 
3,714 

4,808 

6,903 
3,464 
6,141 
2,958 
4,399 

3,993 

Berlin  
High  Bridge.  .  .  . 
Granite  Heights 
Irma  
Granite  City  
Berlin  
Montello  

Granite  Heights 
Amberg  
Knowles 

Bauer's  quarry   

Bridgeport  Stone  Co. 
Gillen  Stone  Co  
Laurie  Stone  Co  
Lee  Bros,  quarry  
Marblehead  Stone  Co. 
Menominee  Falls  Co. 
Giesen  quarry  
Story  quarry  

Bridgeport  

Duck  Creek.  .  .  . 
Sturgeon  Bay 
Genesee 

Marblehead  .... 
Lannon 

Fountain  City.  . 
Wauwatosa  .  . 

Voree  quarry  

Burlington  
Sturgeon  Bay  .  .  . 

Argyle 

Washington  Stone  Co. 

Argyle     Brownstone 
Co. 

Ashland    Brownstone 
Co  
Babcock  &  Smith.  .  .  . 
Bass  Island  B.  Co  
Duluth  Brownstone..  . 
Co  
Dunnville  quarry  
Grover  quarry  

Presque  Isle  .... 
Houghton 

Bass  Island  

Fond  du  Lac  .... 
Dunnville  
LaValle  
Bayfield  

Pike  quarry  
Port  Wing  quarry  
Prentice    Brownstone 
Co. 

Port  Wing  
Houghton 

The  Brard  Test  with  Sodium  Sulphate.  —  In  order  to  obtain 
any  very  striking  results,  actual  freezing  tests  have  to  be  ex- 
tended over  a  long  period  of  time.  To  avoid  this  inconven- 


206  BUILDING   STONES  AND   CLAYS 

ience,  it  was  early  suggested  that  the  effect  of  frost  might  be 
simulated  by  immersing  the  specimen  in  a  saturated  solution  of 
certain  salts,  and  then  allowing  the  absorbed  salts  to  crystallize 
out  of  the  stone.  The  salt  most  commonly  used  for  this  purpose 
is  sulphate  of  soda,  suggested  first  by  Brard,  whose  name  is 
therefore  often  attached  to  the  test. 

The  test  as  carried  out  by  Luquer  was  as  follows: 
A  saturated  cold  solution  of  sulphate  of  soda  was  prepared. 
"  The  specimens,  which  had  been  carefully  prepared,  brushed, 
dried,  and  weighed,  were  boiled  in  the  sulphate  of  soda  for  half 
an  hour,  in  order  to  get  complete  saturation.  At  the  end  of  the 
half  hour  it  was  noticed  in  every  case  that  the  solution  was 
slightly  alkaline,  though  at  the  start  it  had  been  neutral.  In 
order  to  prevent  any  continued  chemical  action  the  beakers  were 
emptied,  the  specimens  rapidly  washed  with  water,  and  the 
beakers  immediately  refilled  with  the  neutral  sulphate  solution. 
After  soaking  for  several  hours,  the  specimens  were  hung  up  by 
threads,  and  left  for  twelve  hours  (during  the  night)  in  a  dark 
room.  In  the  morning  all  the  specimens  were  covered  with  an 
efflorescence  of  the  white  sulphate  of  soda  crystals;  they  were 
then  allowed  to  soak  in  the  solution  during  the  day,  and  again 
hung  up  at  night.  Efflorescing  for  about  twelve  hours  and  soak- 
ing for  about  the  same  time  constituted  a  period.  The  experi- 
ments lasted  for  eight  periods.  .  .  .  During  the  tests  the  solution 
was  renewed  from  time  to  time,  and  appeared  to  remain  neutral. 
The  temperature  of  the  room  varied  from  60°  to  70°  F.  (18°  to 
21°  C.).  Those  specimens  most  affected  began  to  show  the 
disintegrating  action  of  the  solution  very  early  in  the  course  of 
the  experiments.  At  the  end  of  the  ten  (8  ?)  days  the  specimens 
were  sprayed  with  the  stream  from  a  wash  bottle  to  remove  any 
adhering  particles,  washed  in  water  to  remove  the  sulphate  of 
soda,  carefully  dried  in  an  air  bath  at  about  120°  C.  and  weighed 
again." 

These  tests  were  carried  out  in  order  to  determine  whether  or 
not  the  sulphate  of  soda  test  gave  results  directly  comparable 
with  those  obtained  by  actual  freezing,  a  duplicate  series  of 
specimens  being  tested  at  the  same  time  in  the  latter  manner. 
The  results  of  the  two  series  of  tests  are  presented  in  the  follow- 
ing table,  and  it  will  be  seen  that  the  correspondence  is  far  from 
satisfactory. 


LABORATORY  TESTING  OF  STONE 


207 


It  may  also  be  noted  here  that  Gerber*  carried  out  similar 
comparative  tests,  and  that  his  results  were  equally  unsatisfactory . 

TABLE    100.  —  RELATION    OF    FREEZING    AND    SODIUM    SUL- 
PHATE TESTS.     (LUQUER.) 


Kind  of  rock. 

From 

Loss  of  weight. 
Per  cent. 

Ratio 
of  re- 
sults. 
Soda 

Sul- 
phate 
of  soda. 

Freez- 
ing. 

freezing 

Granite  : 
Coarse-grained 

Gallager's,  Me. 

0.1551 
0.0655 
0.0516 
0.0633 
0.0384 

0.0138 

0.0176 

* 

* 

t 

0.0310 
0.0230 
0.0207 

0.1063 
0.1421 
0.6874 
0.0686 

Medium-grained  
Fine-grained  
Fine-grained  gneiss 

Jonesborough,  Me.  .  . 
Hallowell,  Me  
Bedford,  N.  Y  
Keeseville,  N.  Y  

Marble: 
Coarsely-crystalline;  magnesian 
Medium-grained;  magnesian.  .  . 
Fine-grained;  nonmagnesian.  .  .  . 
Sandstone  : 
Fine-grained  

Pleasantville,  N.  Y.  . 
Tuckahoe,  N.  Y  
? 

Belleville,  N.  Y.  . 

(t 

? 

0.1078 
0.1701 
0.2599 

0.4765 
1.4518 
4.8212 
0.2486 

Coarser-grained  
Badly-decomposed 

Pressed  brick 

*  About  same  as  Jonesborough  stone . 
t  Less  than  Jonesborough  stone. 

The  defect  of  the  Brard  test  becomes  apparent  when  the  above 
tests,  or  any  other  long  comparative  series,  are  examined  care- 
fully. The  sulphate  of  soda  method  does  give  measurable 
results  in  short  time.  But  its  results  are  different  from  those  of 
actual  freezing  tests  not  only  in  intensity  but  in  kind.  Chemical 
action  is  introduced  which  attacks  the  specimen  in  a  way  very 
different  from  that  of  frost,  and  the  result  is  that  the  two  tests 
are  in  no  way  comparable.  Inasmuch  as  the  only  excuse  for 
making  the  Brard  test  is  the  idea  that  its  effects  closely  simulated 
those  produced  by  frost,  it  is  evident  that  it  has  failed  in  its 
mission,  and  that  it  requires  no  further  consideration.  It  may 
be  added  that  in  these  days  of  cold-storage  warehouses  it  is  not 
such  a  difficult  matter  to  carry  out  actual  freezing  tests  at  any 
time  of  the  year. 

Resistance  to  Acids.  —  Structural  stone,  particularly  when 
employed  in  manufacturing  cities,  may  be  subjected  to  attack 
by  various  acids  present  in  the  atmosphere.  Carbonic  acid  is 
*  Trans.  Amer.  Soc.  C.  E.,  vol.  33,  p.  253. 


208  BUILDING  STONES  AND  CLAYS 

always  present  in  air,  though  normally  only  in  small  percentages, 
while  nitric,  hydrochloric,  sulphuric,  and  sulphurous  acids  occur 
in  certain  regions. 

Though  these  acids  are  present  in  very  small  amounts,  their 
effect  on  stone,  when  exerted  through  a  long  series  of  years,  may 
be  noticeably  injurious,  and  accordingly  various  tests  have  been 
suggested  to  determine  the  amount  of  this  effect  on  various  kinds 
of  stone. 

In  testing  the  influence  of  carbon  dioxide,  Wilber  *  used  samples 
weighing  about  50  grams.  These  were  dried  at  212°  F.  and 
weighed;  then  placed  on  a  perforated  shelf  under  a  large  bell  jar. 
"  The  bell  jar  was  placed  in  a  shallow  pan,  and  enough  water 
poured  into  the  pan  to  make  a  water  seal  for  the  bell  jar.  Inlet 
and  exit  pipes  were  introduced  into  it  and  a  stream  of  washed 
carbonic  acid  passed  into  the  jar  until  all  air  was  expelled.  The 
openings  were  then  closed  and  the  contents  allowed  to  stand 
three  days  at  a  temperature  of  about  70°  F.  Carbonic  acid  gas 
was  again  passed  in,  and  this  operation  was  repeated,  at  intervals 
during  the  fifty-two  days  of  the  continuance  of  the  test.  The 
samples  were  then  removed  and  soaked  for  four  days  in  distilled 
water,  and  were  afterwards  dried  in  an  air  bath,  at  a  temperature 
of  212°  F.,  to  constant  weight."  The  percentage  of  weight  lost 
during  the  operation  was  then  calculated,  with  the  results  shown 
in  Table  101. 

In  the  course  of  the  New  York  series  of  tests  already  noted, 
Wilber  also  experimented  f  on  the  effects  of  dilute  sulphuric  acid. 
"  Small  cubes,  three-fourths  of  an  inch  on  a  side,  were  used  for 
this  test.  The  samples  were  dried  in  a  water  bath  at  212°  F. 
to  a  constant  weight.  They  were  then  placed  upon  a  perforated 
support  and  immersed  in  dilute  sulphuric  acid.  The  acid  solu- 
tion contained  one  per  cent  of  sulphuric  acid,  H2SO4,  and  the 
volume  used  at  once  was  two  gallons.  After  an  immersion  of 
forty  hours  the  acid  was  drawn  off  and  replaced  by  a  fresh  supply. 
This  remained  upon  the  samples  for  twenty-four  hours,  when  it 
was  run  off  and  a  third  fresh  portion  added,  which  was  allowed 
to  remain  eight  hours.  It  was  then  drawn  off  and  a  gentle 
stream  of  clear  water  passed  through  the  vessel  for  some  time, 
until  the  samples  were  entirely  cleansed  from  the  effects  of  the 

*  Bulletin  10,  N.  Y.  State  Museum,  p.  357  (1890). 
t  Ibid,  p.  358  (1890). 


LABORATORY  TESTING  OF  STONE 


209 


solvent  action  of  the  acid.     They  were  then  carefully  removed 
to  the  water  bath  and  dried  at  212°  F.  to  constant  weight." 

Wilber  also  experimented*  on  the  effect  of  sulphurous  acid  gas. 
These  experiments  were  carried  out  exactly  like  those  in  which 
carbon  dioxide  was  used  (see  page  208),  except  that  the  tests 
lasted  only  thirty-one  days. 

TABLE   101.  — TESTS  WITH  ACIDS.     (WILBER.) 


Stone. 

Locality. 

C02. 

HS2. 

H2SO4. 

Granite 

Grindstone  Is.,  St.  Lawrence  Co.,  N.  Y.  . 
Keeseville  Essex  Co  N  Y 

0.006 
0.002 

0.007 
0.017 

0.13 
0  06 

Hallowell  IMaine 

0.029 

0.024 

0.08 

Marble 

«                « 

Tuckahoe,  Westchester  Co.,  N.  Y  
Pleasantville,  Westchester  Co.,  N.  Y  
Glens  Falls  Warren  Co.,  N.  Y  

0.021 

0.004 
0.005 
0.007 

0.250 
0.150 
0.120 

5.25 
6.63 
2.56 

Limestone 

Gouverneur,  St.  Lawrence  Co.,  N.  Y  

Sandy  Hill,  Washington  Co.,  N.  Y  
Plattsburg,  Clinton  Co.,  N.  Y  

0.017 

0.012 
0.023 

0.150 

0.150 
0.190 

2.63 

2.51 
2.20 

Tribes  Hill,  Montgomery  Co.,  N.  Y  
Canajoharie,  Montgomery  Co.,  N.  Y  
Prospect  Oneida  Co  N  Y 

0.028 
0.012 
0  017 

0.160 
0.160 
0  150 

3.03 

2.62 
2  97 

Chaumont,  Jefferson  Co.,  N.  Y  
Cobleskill,  Schoharie  Co.,  N.  Y  
Onondaga    Reservation,    Onondaga    Co., 
NY.                                             

0.008 
0.010 

0.021 

0.091 
0.130 

0.201 

2.95 

2.58 

2  84 

Union  Springs,  Cayuga  Co.,  N.  Y  
Auburn,  Cayuga  Co.,  N.  Y  
Williamsville,  Erie  Co.,  N.  Y  

0.011 
0.010 
0.060 

0.082 
0.140 
0.250 

3.77 
2.79 
2.97 

Bowling  Green,  Ky  

0.062 

+0.160 

5.66 

Bedford  Ind. 

0  087 

+0  019 

5  83 

C02 

S2 

H2SO4 

Sandstone 

Potsdam  St  Lawrence  Co  N  Y 

0  030 

0  004 

0  02 

Maiden  Ulster  Co  N  Y 

0  032 

0  003 

0  20 

Oxford  Chenango  Co  NY. 

0  021 

0  080 

0  20 

Duanesburgh,  Schenectady  Co.,  N.  Y..  .  . 
Oswego  Falls,  Oswego  Co.,  N.  Y. 

0.011 
0  Oil 

0.065 
0  290 

0.63 
0  74 

Albion,  Orleans  Co.,  N.  Y  
Hulberton,  Orleans  Co.,  N.  Y  

«                                 (I                11                  U 

0.092 
0.046 
0  037 

0.012 
0.061 
0  078 

0.08 
0.08 

Portage,  Wyoming  Co.,  N.  Y  
Warsaw,  Wyoming  Co.,  N.  Y  
Olean,  Cattaraugus  Co.,  N.  Y. 

0.008 
0.015 
0  060 

0.089 
0.250 
0  040 

0.42 
0.49 
0  44 

*  Bulletin  10,  N.  Y.  State  Museum,  p.  358  (1890). 


210 


BUILDING  STONES  AND  CLAYS 


TABLE  101.  — TESTS  WITH  ACIDS.     (WILDER.)     (Continued.) 


Stone. 

Locality. 

C02. 

S2. 

H2S04. 

Sandstone 

East  Longnieadow  IVIass 

0  046 

0  055 

0  12 

0.040 

0.081 
0.086 

0.051 

0.17 

0  076 

0.060 

Portland  Conn 

0.074 
0.053 
0.068 
0  074 

0.146 
0.161 

6  059 

0.11 
0  55 

n              ( 
ti              i 

U                            (( 

Belleville   N  J 

0.080 
0.078 
0.090 
0  031 

0.086 
0.003 

6  040 

0^22 

i  6i 

Berea,  Ohio  

0.066 

0.170 

0.45 

Lake  Superior  Mich. 

0  005 

0  100 

0  36 

Nova  Scotia 

0  025 

0  020 

0  20 

Bristow,  Va.                        

0  079 

0  180 

0  11 

Slate 

Middle  Granville,  Washington  Co.,  N.  Y. 

0.104 
0.004 

0.100 
0.070 

0.07 

Resistance  to  Fire.  —  The  most  complete  series  of  tests  of 
the  fire  resistance  of  building  stones  are  those  by  McCourt,  from 
whose  report  the  following  extracts  are  quoted: 

The  samples  from  each  locality  were  cut  into  three-inch  cubes. 
Most  investigators,  who  have  studied  the  refractoriness  of  build- 
ing stones,  have  selected  one  or  two-inch  cubes;  but  these  sizes 
do  not  give  as  accurate  results  as  the  larger  ones,  for  the  reason 
that  a  small  piece  becomes  easily  heated  throughout  the  mass 
and  consequently  upon  neither  heating  nor  cooling  are  differen- 
tial stresses  between  the  interior  or  exterior  likely  to  be  set  up, 
as  would  be  the  case  if  larger  cubes  are  selected.  In  actual 
fact  in  the  burning  of  a  building  the  stone  does  not  become 
thoroughly  heated;  the  heat  penetrates  probably  but  a  slight 
distance  into  the  mass,  while  the  interior  may  remain  compara- 
tively cold.  The  heating  and  cooling  of  this  outer  shell  causes 
strains  which  do  not  obtain  in  a  stone  which  has  been  heated 
throughout  its  entire  body.  One,  two  and  three-inch  cubes  of 
the  same  kind  of  stone  have  been  tested  in  the  laboratory,  and 
while  the  smaller  cubes  stood  fire  very  well,  the  larger  ones  were 
more  affected  and  in  some  cases  went  to  pieces.  It  was  to  avoid 
this  error  and  to  approach  more  closely  the  existing  conditions 
in  a  conflagration  that  the  three-inch  samples  have  been  em- 
ployed in  the  present  series  of  tests. 


LABORATORY  TESTING  OF  STONE  211 

As  far  as  the  number  of  cubes  would  admit  six  tests  were  made 
on  the  stone  from  each  locality,  four  furnace  and  two  flame  tests. 
For  the  first  set  of  experiments  a  Seger  gas  furnace  was  used, 
thus  allowing  the  cube  to  be  gradually  and  evenly  heated.  An 
opening  was  cut  in  the  cover  of  the  furnace  large  enough  to 
admit  the  three-inch  cube  of  stone,  to  which  a  wire  had  been 
attached  to  facilitate  its  handling. 

One  sample  was  heated  at  a  time.  The  heat  was  applied 
gradually  for  half  an  hour  until  a  temperature  of  550°  C.  was 
reached,  which  was  maintained  for  half  an  hour.  The  tem- 
perature was  measured  with  a  thermoelectric  pyrometer.  The 
cube  was  then  taken  out  and  allowed  to  cool  in  the  air.  A  second 
sample  was  heated,  as  before,  to  550°  C.,  and  this  was  suddenly 
cooled  by  a  strong  stream  of  water.  The  third  and  fourth  cubes 
were  heated  to  850°  C.  kept  at  that  temperature  for  half  an  hour 
and  cooled  slowly  and  suddenly  as  in  the  550°  C.  tests. 

In  order  to  approach  more  nearly  the  conflagration  condi- 
tions samples  were  subjected  to  two  flame  tests.  In  the  first 
case  the  cube  was  so  placed  as  to  be  enveloped  on  three  sides  by 
a  steady  but  not  strong  gas  blast.  The  flame  was  allowed  to 
play  on  the  cube  for  10  minutes,  then  the  samples  were  allowed 
to  cool  for  five  minutes  after  which  time  the  flame  was  again 
applied  for  10  minutes  and  the  cube  was  again  allowed  to  cool. 
To  determine  the  combined  action  of  heat  and  water  a  second 
cube  was  subjected,  as  before,  to  the  flame  for  10  minutes,  then 
a  strong  stream  of  water  was  turned  on  to  the  sample,  along 
with  the  flame,  for  five  minutes.  Then  the  water  was  turned 
off  and  the  flame  continued  for  another  five  minutes,  after  which, 
for  five  minutes  more  the  flame  and  water  together  were  allowed 
to  act  on  the  sample. 

From  the  details  of  the  tests  above  given  some  generaliza- 
tions can  be  drawn  which  are  of  interest  and  of  value.  It  is 
difficult,  however,  to  group  the  different  kinds  of  stone  in  any 
order,  for  they  vary  among  themselves  and  also  act  differently 
under  different  conditions.  A  stone  which  under  some  condi- 
tions stands  up  very  well,  will  disintegrate  under  other  condi- 
tions. Thus,  for  example,  the  granite  from  Northville  acted  very 
badly  on  fast  cooling  after  having  been  heated  to  850°  C.,  yet, 
under  the  combined  action  of  the  flame  and  water,  it  was  little 
damaged.  Additional  variations  of  this  character  are  brought 
out  by  a  close  study  of  the  tables  of  fire  tests,  all  of  which  goes 
to  show  that,  for  one  temperature,  the  order  of  resistance  will 
differ  from  the  order  given  for  another  temperature. 

At  550°  C.  (1022°  F.)  most  of  the  stones  stood  up  very  well. 
The  temperature  does  not  seem  to  have  been  high  enough  to 
cause  much  rupturing  of  the  samples,  either  upon  slow  or  fast 
cooling.  The  sandstones,  limestones,  marble,  and  gneiss  were 


212  BUILDING  STONES  AND  CLAYS 

slightly  injured,  while  the  granites  seem  to  have  suffered  the 
least. 

The  temperature  of  a  severe  conflagration  would  probably 
be  higher  than  550°  C.,  but  there  would  be  buildings  outside  of 
the  direct  action  of  the  fire  which  might  not  be  subjected  to  this 
degree  of  heat  and  in  this  zone  the  stones  would  suffer  little 
injury.  The  sandstones  might  crack  somewhat,  but,  as  the 
cracking  seems  to  be  almost  entirely  along  the  bed,  the  stability 
of  the  structure  would  not  be  endangered,  provided  the  stone 
had  been  properly  set. 

The  gneiss  would  fail  badly,  especially  if  it  were  coarse- 
grained and  much  banded.  The  coarse-grained  granites  might 
suffer  to  some  extent.  These,  though  cracked  to  a  less  extent 
than  the  sandstones,  would  suffer  more  damage  and  possibly 
disintegrate  if  the  heat  were  long  continued  because  the  irreg- 
ular cracks,  intensified  by  the  crushing  and  shearing  forces  on 
the  stone  incident  to  its  position  in  the  structure,  would  tend 
to  break  it  down.  The  limestones  and  marble  would  be  little 
injured. 

The  temperature  of  850°  C.  (1562°  F.)  represents  fairly  the 
probable  degree  of  heat  reached  in  a  conflagration,  though  un- 
doubtedly it  exceeds  that  in  some  cases.  At  this  temperature 
we  find  that  the  stones  behave  somewhat  differently  than  at  the 
lower  temperature.  All  the  cubes  tested  were  injured  to  some 
degree,  but  among  themselves  they  vary  widely  in  the  extent 
of  the  damage. 

All  the  igneous  stones  and  the  gneiss  at  850°  C.  suffered  injury 
in  varying  degrees  and  in  various  ways.  The  coarse-grained  gran- 
ites were  damaged  the  most  by  cracking  very  irregularly  around 
the  individual  mineral  constituents.  Naturally,  such  cracking  of 
the  stone  in  a  building  might  cause  the  walls  to  crumble.  The 
cracking  is  due,  possibly,  to  the  coarseness  of  texture,  and  the 
differences  in  coefficiency  of  expansion  of  the  various  mineral 
constituents.  Some  minerals  expand  more  than  others  and  the 
strains  occasioned  thereby  will  tend  to  rupture  the  stone  more 
than  if  the  mineral  composition  is  simpler.  This  rupturing  will 
be  greater,  too,  if  the  rock  be  coarser  in  texture.  For  example, 
a  granite  containing  much  plagioclase  would  be  more  apt  to 
break  into  pieces  than  one  with  little  plagioclase  for  the  reason 
that  this  mineral  expands  in  one  direction  and  contracts  in 
another,  and  this  would  set  up  stresses  of  greater  proportion 
than  would  be  occasioned  in  a  stone  containing  little  of  this 
mineral.  The  fine-grained  samples  showed  a  tendency  to  spall 
off  at  the  corners.  The  gneiss  was  badly  injured.  In  the  gneisses 
the  injury  seems  to  be  controlled  by  the  same  factors  as  in  the 
granites,  but  there  comes  in  here  the  added  factor  of  banding. 
Those  which  are  made  up  of  many  bands  would  be  damaged 
more  severely  than  those  in  which  the  banding  is  slight. 


LABORATORY  TESTING  OF  STONE  213 

All  the  sandstones  which  were  tested  are  fine  grained  and 
rather  compact.  All  suffered  some  injury,  though,  in  most 
cases,  the  cracking  was  along  the  lamination  planes.  In  some 
cubes,  however,  transverse  cracks  were  also  developed. 

The  variety  of  samples  was  not  great  enough  to  warrant 
any  conclusive  evidence  toward  a  determination  of  the  control- 
ling factors.  It  would  seem,  however,  that  the  more  compact 
and  hard  the  stone  is  the  better  will  it  resist  extreme  heat.  In 
a  general  way  the  greater  the  absorption,  the  greater  the  effect 
of  the  heat.  A  very  porous  sandstone  will  be  reduced  to  sand 
and  a  stone  in  which  the  cement  is  largely  limonite  or  clay  will 
suffer  more  than  one  held  together  by  silica  or  lime  carbonate. 

The  limestones,  up  to  the  point  where  calcination  begins 
(600°-800°  C.),  were  little  injured,  but  above  that  point  they 
failed  badly,  owing  to  the  crumbling  caused  by  the  flaking  of 
the  quicklime.  The  purer  the  stone,  the  more  will  it  crumble. 
The  marble  behaves  similarly  to  the  limestone,  but,  because  of 
the  coarseness  of  the  texture,  also  cracks  considerably.  As  has 
been  mentioned  before,  both  the  limestones  and  marble  on 
sudden  cooling  seem  to  flake  off  less  than  on  slow  cooling. 

The  flame  tests  cannot  be  considered  as  indicative  of  the 
probable  effect  of  a  conflagration  upon  the  general  body  of  the 
stone  in  a  building,  but  rather  as  an  indication  of  the  effect  upon 
projecting  cornices,  lintels,  pillars,  carving,  and  all  thin  edges  of 
stonework.  All  the  stones  were  damaged  to  some  extent.  The 
granites  from  Keeseville  and  Northville  stood  up  very  well;  the 
limestones  were,  as  a  whole,  comparatively  little  injured,  while 
the  marble  was  badly  damaged.  The  tendency  seems  to  be  for 
the  stone  to  split  off  in  shells  around  the  point  where  the  greatest 
heat  strikes  the  stone.  The  temperature  of  the  flame  probably 
did  not  exceed  700°  C.,  so  it  is  safe  to  say  that  in  a  conflagration 
all  carved  stone  and  thin  edges  would  suffer.  However,  outside 
of  the  intense  heat,  the  limestones  would  act  best,  while  the 
other  stones  would  be  affected  in  the  order:  sandstone,  granite, 
gneiss,  and  marble. 

After  having  been  heated  to  850°  C.  most  of  the  stones,  as 
observed  by  Buckley,*  emit  a  characteristic  ring  when  struck 
with  metal  and  when  scratched  emit  a  sound  similar  to  that  of 
a  soft  burned  brick.  It  will  be  noted  that  in  those  stones  in 
which  iron  is  present  in  a  ferrous  condition  the  color  was  changed 
to  a  brownish  tinge  owing  to  the  change  of  the  iron  to  a  ferric 
state.  If  the  temperature  does  not  exceed  550°  C.,  all  the  stones 
will  stand  up  very  well,  but  at  the  temperature  which  is  probable 
in  a  conflagration,  in  a  general  way,  the  finer-grained  and  more 
compact  the  stone  and  the  simpler  in  mineralogic  composition 
the  better  will  it  resist  the  effect  of  the  extreme  heat.  The  order, 

*  Mo.  Bureau  Geol.  and  Mines,  Ser.  2  (1904),  2:50. 


214  BUILDING  STONES  AND  CLAYS 

then,  of  the  refractoriness  of  the  New  York  stones  which  were 
tested  might  be  placed  as  sandstone,  fine-grained  granite,  lime- 
stone, coarse-grained  granite,  gneiss,  and  marble. 

IV.  TESTS  TO  DETERMINE  STRENGTH. 

Crushing  Strength.  —  It  has  often  been  pointed  out  that  no 
stone  which  an  engineer  is  likely  to  use  will  ever  fail  by  crushing, 
for  even  in  such  massive  masonry  structures  as  the  Washington 
Monument  and  the  Brooklyn  Bridge  piers  the  compression  per 
square  inch  at  the  base  is  much  below  that  which  even  a  rela- 
tively weak  building  stone  will  bear.  It  is  pointed  out,  more- 
over, that  though  a  small  test  piece  of  a  given  limestone  may 
fail  by  crushing  at,  say,  12,000  pounds  per  square  inch,  every 
natural  exposure  of  the  rock  proves  to  us  that  in  larger  masses 
it  is  practically  uncrushable.  In  spite  of  these  facts,  the  test 
most  commonly  carried  out,  when  quality  of  a  stone  is  in  question, 
is  that  for  crushing  strength. 

Even  though  this  test  be  unnecessary,  it  could,  if  carried  out 
uniformly,  give  us  certain  information  of  value,  and  be  a  means 
of  comparing  the  strength  of  different  stones.  Unfortunately, 
however,  there  is  at  present  little  uniformity  in  the  matter.  The 
apparent  "  compressive  strength  per  square  inch,"  as  shown  by 
any  given  stone  in  the  testing  machine,  is  known  to  vary  with 
the  shape  of  the  test  piece,  its  size,  and  the  character  of  the 
bearing  surfaces;  but  sufficient  experiments  have  not  been  car- 
ried out  to  determine  the  laws  of  these  variations. 

In  the  matter  of  size  of  test  piece,  Gillmore's  earlier  experi- 
ments seemed  to  prove  that  a  large  cube  gave  higher  compressive 
resistance  per  square  inch  than  a  small  cube,  and  he  constructed 
a  formula  showing  the  variation  in  compressive  strength  in 
relation  to  size  of  cube.  This  formula  will  frequently  be  found 
quoted  in  engineering  and  geological  treatises,  though  within  a 
year  of  its  announcement  Gillmore  had  determined,  from  the 
results  of  a  longer  series  of  experiments,  that  the  so-called  law 
did  not  hold  true. 

Regarding  the  shape  of  test  piece,  it  has  been  determined  that 
a  prism  whose  height  is  one  and  one-half  times  the  width  of  its 
base  will  give  far  more  accurate  results  than  the  cube.  This 
determination  has  had  little  effect  on  testing  practice,  however, 
the  cube  being  employed  as  heretofore. 


LABORATORY  TESTING  OF  STONE 


215 


TABLE  102.*  — EFFECT  OF  BEARING  MATERIALS  ON 
STRENGTH  OF  SANDSTONE.     (BEARE.) 


Name  of  stone. 

Average  compressive 
strength. 

Loss  of 
strength  due 
to  lead,  per 
cent. 

Plaster  of 
Paris, 
pounds  per 
square  inch. 

Lead  sheet, 
pounds  per 
square  inch. 

Binnie                                             

6,339 
6,115 
10,382 
8,682 
13,408 

3,942 
3,942 
4,637 
4,995 
6,361 

37.8 
35.5 
55.3 
42.5 
52.6 

Hermand       

White  Hailes  

Arbroath  ,  

Craigleith 

*  Proc.  Institution  Civil  Engineers,  vol.  107,  p.  344. 

TABLE  103.— EFFECT  OF  POSITION  ON   CRUSHING 
STRENGTH  OF  STONE. 


Ult.  compr. 

Kind  of  rock. 

Locality. 

Tested  by 

Size  of 
cube. 

strength,  Ibs. 
per  sq.  in. 

Ratio, 
bed 
-5-  edge. 

Bed. 

Edge. 

Syenite 

French  Creek,  Pa  

R.  L.  Humphrey... 

In. 

8 

17,274 

7,910 

2.18 

2 

19,997 

14,348 

1.38 

Gneiss,  light  color 

Chester,  Pa  

8 

9,505 

6,426 

1.48 

li                     ** 

2 

6,097 

5,446 

1.12 

Gneiss,  dark  color 

Germantown,  Pa  

8 

11,636 

13,984 

0.83 

"             *• 

2 

19,891 

15,555 

1.28 

Holmesburg,  Pa  

Lathbury  &  Spack- 

man  

5* 

21,684 

19,527 

1.11 

Mica  schist 

Conshohocken,  Pa.  ... 

R.  L.  Humphrey  .  .  . 

8 
2 

10,417 
20,038 

7,532 
15,680 

1.38 
1.28 

Roofing  slate 

Brownville,  Me  

Mass.  Inst.  Tech  

1 

29,270 

16,750 

1.75 

Sandstone 

Curwensville,  Pa  

R..  L.  Humphrey 

8 

7,513 

4,463 

1.68 

"             " 

"             ** 

2 

10,218 

8,013 

.27 

Irumberville,  Pa  

«             it 

8 

14,841 

8,637 

.72 

1/angford,  Ky. 

Vatertown  Arsenal  .  . 

2 
2 

15,135 
27,703 

12,341 
22,923 

.23 
.29 

Albion,  N.  Y  

Berlin  Hts.,  Ohio  

Gillmore  

3 

14,250 

12,000 

.19 

Limestone 

Bowling  Green,  Ky.  .  . 

Vatertown  

5 

6,998 

6,387 

1.10 

TABLE  104.  — EFFECT  OF  METHOD  OF  DRESSING  CUBES.* 


Modulus  c 

1 

Rupture. 

Compres- 
sion. 

Elasticity. 

Sawed  specimens,  average  
Tool-dressed  specimens,  average  

2,338 
1,477 

12,675 

7  857 

4,889,480 
2  679  475 

Ratio  of  strength,  tool-dressed  -5-  sawed..  . 

63% 

62% 

55% 

*  llth  Ann.  Rep.  Indiana  Dept.  Geology,  p.  39  (1881). 


216  BUILDING  STONES  AND  CLAYS 

Transverse  Strength.  —  Little  attention  is  usually  paid  to 
testing  the  transverse  strength  of  building  stones,  except  in  the 
case  of  stones  intended  for  use  as  flagging,  lintels,  etc.  This 
neglect  is  the  more  curious  because  building  stone,  in  actual  con- 
struction, often  fails  under  transverse  strain,  as  may  be  seen  in 
the  walls  of  many  buildings.  In  theory,  of  course,  a  building 
should  be  so  constructed  as  never  to  subject  its  wall  material  to 
anything  but  a  direct  compressive  strain.  In  practice,  however, 
the  case  is  very  different.  Owing  to  bad  masonry  work,  or  more 
generally  to  the  unequal  settlement  of  foundations,  '  transverse 
strains  do  frequently  occur,  and  their  effect  is  shown  by  vertical 
cracks  in  the  poorer  or  weaker  stones  of  the  walls. 

In  determining  transverse  strength  the  formula  used  is: 


in  which  formula 

R  =  modulus  of  rupture  in  pounds  per  square  inch. 
W  =  concentrated  load  at  center  in  pounds. 
L  =  length  between  supports,  in  inches. 
B  =  breadth  in  inches. 
D  =  depth  in  inches. 

Hardness.  —  The  resistance  of  stone  to  mechanical  wear  is 
rarely  of  sufficient  importance  to  justify  testing,  when  the  stone 
is  used  strictly  as  a  building  material.  Flagging,  steps,  and  sills 
are,  however,  subjected  to  considerable  wear,  and  it  is  possible 
that  some  simple  abrasion  test  might  be  of  service.  The  only 
structural  stone,  however,  that  really  fails,  owing  to  ordinary 
mechanical  wear,  is  serpentine,  which  is  entirely  too  soft  to  be 
used  in  any  unprotected  situation. 

LIST  OF  REFERENCES  ON  TESTS  OF  BUILDING  STONE. 

In  addition  to  such  general  works  as  those  of  Gillmore,  Merrill,  Johnson 

and  the  Watertown  Arsenal  reports,  the  references  in  the  following 

list  may  be  found  serviceable. 
Bach,  C.     Experimental  investigations  upon  granite.     Zeits.  der  Verein 

Deutscher  Ingen.,  Feb.  27,  1897. 
Bach,  C.    The  relation  between  extension  and  strength  in  sandstone. 

Zeits.  der  Ver.  Deutsch.  Ingen.,  Sept.  1,  1900. 
Buckley,  E.  R.     Building  and  ornamental  stones  of  Wisconsin.     Bull.  4, 

Wisconsin  Geol.  Sur.     1898. 


LABORATORY  TESTING  OF  STONE  217 

Garrison,  E.  L.     Notes  upon  testing  building  stone.     Trans.  Am.  Soc. 

C.  E.,  vol.  32,  pp.  87-98.     1894. 
Gary,  M.     The  testing  of  natural  stone  in  the  years  1895-1898.     Mitt- 

heilung  aus  der  Konig.  Tech.  Versuchsanhalten,  No.  5.     1898. 
Greenleaf,  J.  L.     Building  stones.     School  of  Mines  Quarterly,  vol.  1, 

pp.  27-39,  52-63.     1880. 
Griibler,  M.     The  strains  in  grindstones  and  emery  wheels.     Zeits.  der 

Verein  Deutscher  Ingen.,  July  24,  1897. 
, .     Experiments  upon  the  strength  of  grindstones.     Zeits.  der 

Verein  Deutscher  Ingen.,  Oct.  21,  1899. 
Hall,  J.     Report  on  building  stones.     39th  Ann.  Rep.  New  York  State 

Museum,  pp.  186-225.     1886. 
Howe,  M.  A.     Experiments  to  determine  the  effect  of  the  bedding  material 

on  the  strength  of  marble.     Engineering  News,  Feb.  15,  1894.  , 
Johnson,  T.  H.     Experiments  upon  the  transverse  strength  and  elasticity 
of  building  stone,     llth  Ann.  Rep.  Indiana  Dept.  Geol.,  pp.  34-42. 
1882. 

Julien,  A.  A.     Building  stones  —  elements  of  strength  in  their  constitu- 
tion and  structure.     Jour.  Franklin  Institute,  vol.  147,  pp.  257-286, 

378-397,  430-442.     1899. 
Luquer;  L.  M.     The  relative  effects  of  frost  and  the  sulphate  of  soda  tests 

on  building  stones.     Trans.  Am.  Soc.  C.  E.,  vol.  33,  pp.  235-256. 

1895. 
Merrill,    G.    P.     The   physical,    chemical,  and   economic   properties   of 

building  stones.     Reports  Maryland  Geol.  Sur.,  Vol.  2,  pp.  47-123. 

1898. 
Perry,  G.  W.     The  relation  of  the  strength  of  marble  to  its  structure. 

Engineering  News,  vol.  52,  p.  45.     1891. 

Raymond,  C.  A.,  and  Cunningham,  E.  W.     Building  stone.     Engineer- 
ing News,  March  28,  1895. 
Smock,  J.  C.     Building  stone  in  New  York.     Bull.   10,  N.  Y.  State 

Museum,  396  pp.     1890. 


PART   II.     CLAYS. 


CHAPTER  XIII. 
CLAYS:   GENERAL  CLASSIFICATION. 

Definitions  of  Clay,  Shale,  and  Slate.  —  The  term  clay  is 
applied  to  fine-grained  unconsolidated  natural  materials  which 
possess  the  property  of  plasticity  when  wet,  while  they  lose  this 
property  and  harden  on  being  strongly  heated.  Clays  are  readily 
molded  in  all  desirable  shapes  when  wet;  and  this  property  is  one 
factor  in  the  usual  commercial  definition  of  a  clay:  though  the 
typical  kaolins  are  not  plastic.  Since  the  clays  are,  as  described 
below,  the  finer  debris  resulting  from  the  decay  of  many  different 
kinds  of  rocks,  they  will  naturally  differ  greatly  among  themselves 
as  regards  composition,  properties,  etc.,  and  these  differences 
prevent  the  formulation  of  a  more  precise  definition. 

Clays  are  rock  material  in  an  exceedingly  fine  state  of  subdi- 
vision, ultimately  derived  from  the  decay  of  older  rocks,  the 
finer  particles  resulting  from  this  decay  being  carried  off  and 
deposited  by  streams  along  their  channels,  in  lakes,  or  along 
parts  of  the  sea  coast  or  sea  bottom  as  beds  of  clay.  In  chemical 
composition  the  clays  are  composed  essentially  of  silica  and 
alumina,  though  iron  oxide  is  almost  invariably  present  in  more 
or  less  amount,  while  lime,  magnesia,  alkalies,  and  sulphur  are 
of  frequent  occurrence,  though  usually  only  in  small  percentages. 

The  materials  known  respectively  as  shales  and  slates  are  of 
practically  the  same  composition  and  ultimate  origin,  but  differ 
in  their  degree  of  consolidation. 

Shales  are  clays  which  have  become  hardened  by  pressure. 
The  so-called  "  fire  clays  "  of  the  coal  measures  are  shales,  as 
are  many  of  the  other  "  clays  "  of  commerce.  The  slates  include 
those  clayey  rocks  which  through  pressure  have  gained  the 
property  of  splitting  readily  into  thin  parallel  leaves. 

218 


CLAYS:   GENERAL  CLASSIFICATION  219 

Origin  of  Clays ;  General  Statement.  —  When  rocks  of  any 
kind  are  exposed  to  atmospheric  action,  more  or  less  rapid  disin- 
tegration sets  in.  This  is  due  partly  to  chemical  and  partly  to 
physical  causes.  It  is  hastened,  for  example,  by  the  dissolving 
out  of  any  soluble  minerals  that  may  occur  in  the  rock,  by  the 
expansion  and  contraction  due  to  freezing,  and  by  the  action  of 
the  organic  acids  set  free  by  decaying  vegetable  matter.  The 
more  soluble  ingredients  of  the  rock  are  usually  removed  in 
solution  by  surface  or  percolating  waters,  while  the  more  in- 
soluble portions  are  either  left  behind  or  are  carried  off  mechani- 
cally by  streams.  These  relatively  insoluble  materials,  when 
sufficiently  fine-grained,  constitute  the  clays.  When  they  are 
left  as  a  deposit  in  the  spot  where  the  original  rock  disintegrated 
they  are  called  residual  clays,  while  if  they  have  been  removed 
from  the  site  of  the  present  rock  they  are  termed  transportation 
clays.  If  the  materials  are  carried  off  mechanically  by  surface 
waters  and  finally  deposited  along  river  beds,  in  lakes,  or  in  the 
sea  they  are  termed  transported  or  sedimentary  clays.  In  a  third 
class,  of  limited  areal  distribution  but  of  considerable  importance 
where  they  occur,  are  the  glacial  clays  which  owe  their  position 
to  the  great  ice  sheets  which  formerly  covered  most  of  the  north- 
ern portion  of  the  United  States,  the  clays  in  question  having 
been  deposited  under  or  in  front  of  these  glaciers.  A  class  of 
still  more  limited  extent  and  importance  includes  the  eolian  or 
wind-borne  clays,  the  example  usually  quoted  being  the  loess 
clays,  which  are  supposed  by  some  geologists  to  have  been 
transported  and  deposited  by  the  winds. 

So  far  as  origin  is  concerned,  clay  deposits  are  therefore  due 
to  the  cooperation  of  two  sets  of  agencies  —  chemical  and  me- 
chanical. With  regard  to  the  residual  clays,  chemical  agencies 
have  in  some  cases  been  the  more  important ;  but  the  transported 
or  sedimentary  clays  are,  in  their  present  deposits,  due  almost 
entirely  to  purely  mechanical  causes. 

Classification  Based  on  Origin.  —  The  facts  which  have  been 
briefly  stated  above  naturally  lead  toward  a  classification  of 
clays  based  on  the  methods  of  origin  and  of  deposition.  A  satis- 
factory working  classification  of  this  type  is  presented  below  in 
outline  form;  after  which  each  of  the  groups  named  in  this  outline 
will  be  separately  discussed  in  more  detail. 

A.   Residual    clays,    resulting   from    the   decay   in   place   of 


220  BUILDING  STONES  AND   CLAYS 

igneous  rocks,  of  shales,  or  of  clayey  limestones.     This  group 
may  be  subdivided  into  three,  according  as  the  clay  is  derived. 

1.  From  the  decay  of  igneous  rocks. 

2.  From  the  decay  of  shales  or  slates. 

3.  From  the  decay  of  more  or  less  clayey  limestone. 

B.  Transported  clays,  resulting  from  the  transportation  by 
water  (or  more  rarely  by  ice  or  wind)  of  both  the  residual  clays 
of  Class  A  and  of  all  sorts  of  finely-ground  rock  material,  and 
the  deposition  of  this  material  at  favorable  points  more  or  less 
distant  from  its  point  of  origin.  The  clays  of  this  class  may  be 
subdivided  according  to  their  method  of  transportation,  their 
point  of  deposition,  or  their  present  physical  state.  A  sub- 
classification  recognizing  these  three  factors  is  as  follows: 

1.  Water-borne  clays;  transportation  effected  by  water. 

(a)    Marine  clays,  deposited  in  salt-water  basins. 

1.  Marine  clays  proper  (i.e.,  soft  clays). 

2.  Shales. 

3.  Slates. 

(6)    Stream    clays,    deposited    along    the    courses    of 

streams  or  rivers. 
(c)    Lake  clays,  deposited  in  lakes  or  ponds. 

2.  Ice-borne  or   glacial   clays;    transportation   effected  by 

glacial  ice. 

3.  Wind-borne  or  eolian  clays;  transportation  effected  by 

the  wind. 


CHAPTER  XIV. 
RESIDUAL   CLAYS. 

Origin  of  Residual  Clays.  —  The  residual  clays  owe  their 
origin  to  the  decay  or  disintegration  of  some  rock  mass  under 
the  action  of  natural  agencies,  and  to  the  consequent  accumu- 
lation of  the  more  insoluble  or  resistant  portions  as  a  residual 
material  on  the  surface  of  the  parent  rock.  The  natural  agents 
which  effect  this  decay  and  disintegration  may  be  either  chemical 
or  mechanical  —  usually  both  sets  of  forces  are  at  work.  The 
manner  in  which  the  decay  and  disintegration  of  the  rock  are 
produced  will  depend  on  the  character  of  the  agent  and  on  the 
character  of  the  rock.  The  methods  of  action  and  the  effects 
produced  are  so  different,  on  different  types  of  rock,  that  it 
seems  advisable  to  discuss  the  subject  under  three  special  head- 
ings, each  of  which  will  cover  the  formation  of  an  important  class 
of  clay  deposits.  By  far  the  majority  of  residual  clays  are  de- 
rived from  the  decay  of  igneous  rocks,  of  shales,  or  of  clayey 
limestones  —  for  the  sandstones  rarely  yield  clay  deposits  of 
any  kind. 

Residual  from  Decay  of  Igneous  Rocks.  —  The  igneous  rocks 
usually  contain  a  number  of  minerals,  some  of  which  are  com- 
paratively unaffected  by  weathering,  while  others  yield  with 
considerable  rapidity.  A  granitic  rock  may  be  taken  for  ex- 
ample, composed  of  quartz,  feldspar,  mica,  and  probably  a  little 
hornblende.  When  a  rock  of  this  character  is  exposed  at  the 
surface,  its  quartz  would  be  practically  unaffected  by  the  ordinary 
weathering  agents;  its  feldspar  would  decay  with  comparative 
rapidity,  while  its  mica  and  hornblende  would  also  alter,  though 
less  strikingly  than  the  feldspar.  Extremes  of  cold  and  heat 
would  tend  to  disintegrate  the  rock  physically,  and  so  make  its 
minerals  more  open  to  attack  from  percolating  waters  carrying 
dissolved  acids. 

The  decay  of  feldspars  undoubtedly  gives  rise  to  certain  clay 
deposits  of  interesting  type,  and  though  the  importance  of  this 

221 


222 


BUILDING  STONES  AND   CLAYS 


fact  has  been  greatly  exaggerated  in  clay  literature,  the  subject 
is  worth  some  consideration  here. 

The  feldspars  are  essentially  silicates  of  alumina  and  potash, 
soda  or  lime.  The  composition  of  the  different  feldspar  species 
is  discussed  in  some  detail  on  page  25,  to  which  reference  should 
be  made  for  further  data  on.  the  subject.  In  the  present  case  it 
will  be  sufficient  to  take  up  the  most  familiar  variety  of  feldspar 
—  orthoclase  —  and  to  trace  the  changes  which  it  undergoes 
during  chemical  decay. 

Orthoclase  has  the  formula  K2O,  A12O3,  6  SiO2,  corresponding 
in  composition  to  silica  64.60  per  cent,  alumina  18.50  per  cent, 
potash  16.90  per  cent.  When  exposed  to  the  action  of  waters 
carrying  in  solution  carbonic,  sulphuric,  and  organic  acids,  a 
chemical  decomposition  of  the  mineral  takes  place,  resulting  in 
the  removal  of  the  potash  and  most  of  the  silica  (and  of  any 
lime  or  iron  that  may  be  present),  the  formation  of  a  hydrous 
aluminum  silicate,  and  the  segregation  of  the  residual  silica. 
The  aluminum  silicate  thus  formed  may  be  any  one  of  a  long 
series  —  of  which  kaolinite  and  pholerite  are  probably  the  most 
prominent.  The  chemical  relationship  existing  between  the 
original  feldspar  and  these  two  possible  final  products  is  shown 
in  the  following  comparative  table. 

TABLE  105.  — COMPOSITION  OF  ORTHOCLASE,  KAOLINITE, 
AND  PHOLERITE. 


Orthoclase. 

Kaolinite. 

Pholerite. 

Silica  (SiO2)  
Alumina  (A12O3)  
Potash  (K2O) 

64.6 

18.5 
16  9 

46.3 
39.8 

39.3 
45.0 

Combined  water.  .  .  . 
Formula  

Specific  gravity 

k2b,'Ai2o3r6si62 

2  57 

13.9 
A12O3,  2  SiO2, 
+  H20 
2.5 

15.7 

2Al2O3,3SiO2, 
+  4H20 

Pure  kaolinite  and  pholerite  are  plastic,  highly  refractory, 
white-burning  materials.  As  formed  by  the  decay  of  granitic 
rocks,  however,  the  products  are  impure,  containing  grains  or 
masses  of  the  relatively  insoluble  constituents  of  the  granite, 
i.e.,  quartz,  mica,  hornblende,  etc.  These  impurities  operate 
to  reduce  the  plasticity  and  refractoriness  of  the  product,  and 
often  to  alter  its  color  when  burnt  to  yellow  or  even  red.  Of 


RESIDUAL  CLAYS 


223 


course  the  less  quartz  and  mica  contained  in  the  original  rock 
the  purer  would  be  the  product,  and  the  ideal  kaolinite  (or 
pholerite)  would  therefore  result  from  the  decay  of  a  vein  of 
pure  feldspar. 

All  that  has  been  said  in  the  above  paragraphs  concerning  the 
chemical  decay  of  feldspar  must  be  read  with  the  understanding 
that  this  is  only  one  phase  of  the  weathering  of  an  igneous  rock,, 
and  that  often  it  is  not  even  an  important'phase.  To  ascribe  all 
clay  deposits,  ultimately,  to  such  an  origin  is  simply  to  misunder- 
stand the  very  obvious  facts  of  the  case.*  Purely  mechanical 
disintegration  always  plays  a  large  part  in  the  weathering  of 
such  rocks,  and  at  times  it  is  the  only  important  agent.  Many 
residual  materials  will  be  found  which  show  little  sign  of  chemical 
alterations  or  changes,  and  differ  from  the  unweathered  rock 
only  in  the  fact  that  they  are  now  fine,  unconsolidated  products 
instead  of  the  original  mass  of  interlocking  crystals. 

TABLE  106.  —  ANALYSES  OF  ACID  IGNEOUS  ROCKS  AND 
RESIDUAL  CLAYS. 


la. 

16. 

2a. 

26. 

Silica  (SiO2)  

66  31 

56  40 

69  88 

51  29 

Alumina  (Al2Os)  

18  27 

25  62 

16  42 

OQ  fiQ 

Ferrous  oxide  (FeO)  { 

2  51 

3  45 

1  96 

6  33 

rerric  oxide  (Fe^Os)  i 
Lime  (CaO)  

2  91 

0  37 

1  78 

0  07 

Magnesia  (MgO)  
Potash  (K2O)  .  . 

1.22 
4  09 

0.98 
2  99 

0.36 

K    AQ 

0.14 

1    ^0 

Soda  (Na2O)  

3  69 

1  36 

4  4fi 

1    19 

Combined  water.  .  .    . 

0  61 

9  18 

0  36 

10  3fi 

16.   Residuary)    Camak>  Georgia.    Bull.  9,  Georgia  Geol.  Sur.,  p.  321. 
2o, 

26. 


J,      AbOBKUUAI   \j±O,y  ) 

I'.   Residuary)    Greenville»  Georgia.    Bull.  9,  Georgia  Geol.  Sur.,  p.  315. 

The  character  of  the  residual  clay  resulting  from  the  decay  of 
an  igneous  rock  depends  partly  on  the  composition  of  the  original 
rock,  and  partly  on  the  degree  to  which  decomposition  has  pro- 

*  Of  recent  American  writers  on  the  origin  of  clays,  only  one  has  treated 
this  subject  with  thorough  knowledge  and  a  due  sense  of  proportion;  and 
the  reader,  desirous  of  making  a  more  detailed  study  of  this  phase  of  the 
subject  will,  therefore,  do  well  to  consult  G.  P.  Merrill's  "Rocks  Rock 
Weathering,  and  Soils." 


224 


BUILDING  STONES  AND  CLAYS 


The  effect  of  the  second  of  these  factors  is  of  course 
obvious,  but  the  first  requires  some  further  consideration. 

The  acid  igneous  rocks  —  such  as  the  granites  —  are  rela- 
tively high  in  silica,  and  low  in  iron  oxide,  lime,  magnesia,  and 
alkalies.  The  clays  which  result  from  the  decomposition  and 
disintegration  of  such  rocks  are  apt,  therefore,  to  be  low  in  the 
last-named  constituents. 

The  basic  igneous  rocks  —  traps,  gabbros,  etc.  —  being  origi- 
nally low  in  silica  and  relatively  high  in  iron,  lime,  magnesia,  and 
alkalies,  give  usually  much  more  impure  residual  clays  than  do 
the  acid  rocks.  Even  when  chemical  action  (solution)  has  been 
most  thorough,  much  or  all  of  the  iron  oxide  is  left  behind  in 
the  clay;  though  the  lime,  magnesia,  and  alkalies  of  the  original 
rock  may  appear  in  greatly  lessened  percentages  in  the  residual 
material.  Where  mechanical  disintegration  has  played  much 
part  in  the  process,  however,  then  fluxing  impurities  remain  in 
the  residual  product. 

Basic  rocks  do  not  occur  at  the  earth's  surface  in  such  great 
masses  as  the  more  acid  types,  nor  are  they  so  widely  distributed. 
Because  of  these  facts,  clays  derived  from  basic  rocks  are  not 
of  very  common  occurrence  or  of  great  importance  to  the  clay 
industries. 

TABLE   107.  —  ANALYSES  OF  BASIC  IGNEOUS  ROCKS  AND 
RESIDUAL  CLAYS. 


la. 

16. 

2a. 

26. 

Silica  (SiO2) 

46  75 

42  44 

38  85 

38  82 

Alumina  (A12O3)  
Iron  oxide  (Fe2Os)  

17.61 
16.79 

25.51 
19.20 

12.77 
12.86 

22.61 
13  33 

Lime  (CaO)  

9.46 

0.37 

6.12 

6.13 

Magnesia  (MgO) 

5  12 

0  21 

22  58 

9  52 

Potash  (K2O)                    

0.55 

0  49 

0  19 

0  18 

Soda  (Na2O)  
Water  

2.56 
0.92 

0.56 
10.92 

0.11 
6.52 

0.20 
9  21 

la.  Fresh  diorite  )   Albermarle  County,  Va.    G.  P.  Merrill,  "  Rocks,  Rock 

16.  Residual  clay)       Weathering,  and  Soils,"  p.  225. 

2a.  Fresh  pyroxenite )    Albermarle  County,  Va.     G.  P.  Merrill,  "  Rocks, 

26.  Residual  clay       )       Rock  Weathering,  and  Soils/'  p.  226. 

Residual  from  Decay  of  Shales  or  Slates.  —  Since  shales  and 
slates  are  formed  simply  by  the  consolidation  of  clay  beds,  it  is 
obvious  that  simple  mechanical  disintegration  of  a  bed  of  shale 


RESIDUAL  CLAYS 


225 


will  cause  it  to  again  become  a  bed  of  clay.  So  that  wherever 
shale  beds  are  exposed  to  weathering  we  find  that  along  the  out- 
crop the  shales  have  broken  down  and  become  soft  and  plastic. 
Often  the  change  has  gone  further  than  simple  disintegration, 
for  during  the  physical  decay  of  the  shale  percolating  waters  may 
have  removed  some  of  its  more  soluble  constituents. 
TABLE  108.  —  ANALYSES  OF  CLAYS  RESIDUAL  FROM  SHALE. 


1. 

2. 

3. 

4. 

5. 

Silica  (SiO2) 

71  91 

73.30 

84  05 

72  16 

47  00 

Alumina  (Al2Os) 

16.24 

14.49 

9  44 

21  76 

38  75 

Iron  oxide  (Fe2Os)    ...             . 

1.79 

1.26 

0.28 

0.99 

0  95 

Lime  (CaO)  
Magnesia  (MgO)  
Alkalies  (K2O,  Na2O)  

0.18 
0.88 
3.27 

0.19 
2.14 
4.31 

0.23 
1.35 
2.65 

0.22 
0.70 
5.14 

0.70 
tr. 
tr. 

Carbon  dioxide  (CO2) 

Combined  water  . 

4  39 

3  57 

2  18 

4  76 

12  94 

1.  Hot  Springs,  Ark.     Average  of  four  analyses  by  Geo.  Steiger.     Bull. 

285,  U.  S.  Geol.  Sur.,  p.  409. 

2.  Mountain  Valley,   Ark.     Average  of  two  analyses  by  Geo.   Steiger. 

Bull.  285,  U.  S.  Geol.  Sur.,  p.  409. 

3.  Upper  Mill,  Pa.     Hopkins,  Clays  of  Pennsylvania,  pt.  3,  p.  10. 

4.  Fogelsville,  Pa.     Hopkins,  Clays  of  Pennsylvania,  pt.  3,  p.  10. 

5.  Valley  Head,  Ala. 

Clays  formed  by  the  decay  of  beds  of  shale  or  slate  are  apt 
to  contain  little  foreign  matter  except,  perhaps,  an  occasional 
fragment  of  unweathered  shale.  Of  course  these  fragments  are 
rare  near  the  surface  but  become  more  common  in  the  deeper 
parts  of  the  clay  deposit,  as  the  unweathered  portion  of  the  rock 
is  approached.  Even  where  frequent,  however,  they  do  not  in- 
jure the  value  of  the  deposit,  for  the  unweathered  fragments  of 
shale  are  of  practically  the  same  compo- 
sition as  the  bed  of  residual  clay  which 
is  derived  from  the  weathering  of  thr 
shale. 

The  form  taken  by  such  deposits  oi 
clay  (i.e.  residual  from  shales  or  slates), 
depends  largely  on  the  attitude  of  the 
original  shale  bed  and  on  the  topography 
of  the  district.  If  the  shale  bed  was 
highly  inclined  to  the  horizon  and  outcropped  along  a  hillside 
(as  in  Fig.  24) ,  percolating  water  and  atmospheric  agencies  might 


226 


BUILDING  STONES  AND  CLAYS 


Fig.  25.  —  Interbedded  shales   and 
limestone. 


readily  disintegrate  the  shale  for  some  distance  down  from  the 
outcrop.     The  resulting  clay  deposit  would  still  be  in  the  form 

of  a  bed,  with  a  dip  corresponding 
to  that  of  the  original  shale  bed. 
In  one  particular  case,  however, 
a  very  marked  change  in  atti- 
tude may  be  brought  about  by 
the  weathering  of  the  rocks;  and 
this  special  case  is  of  much  im- 
portance since  it  has  given  rise 

^  valuable    clay    deposits 

.  *  J.        .      . 

in  southeastern  Pennsylvania,  in 

Alabama,  and  elsewhere.  The  case  in  question  is  when  the 
shale  was  originally  inter  bedded  with  limestone,  both  series  of 
rocks  dipping  at  an  angle  of 
15  degrees  to  50  degrees.  The 
effect  of  weathering  on  such 
an  outcrop  is  twofold,  for  while 
the  shale  weathers  into  clay, 
most  of  the  limestone  is  dis- 
solved, so  that  the  soft  clay 
beds  gradually  sink  down  to 
form  a  thick  and  irregularly-shaped  deposit.  This  deposit  con- 
tains not  only  the  softened  shale,  but  also  any  insoluble  material 
that  was  contained  in  the  original  limestone.  When  such  a  clay 
deposit  is  examined,  therefore,  masses  of  fairly  pure  shale  clay 
will  be  found  inclosing  layers  of  less  pure  and  limestone  residual, 
often  containing  fragments  or  nodules  of  chert  or  flint. 

If  the  shale  bed  had  been  horizontal  or  nearly  so,  and  were 
now  exposed  along  a  valley  bottom,  the  clay  deposit  would 
probably  be  more  irregular  in  thickness,  as  indicated  in  Fig.  27. 


Fig.  26.  —  Effect  of  weathering  on  shale- 
limestone  strata. 


Fig.  27.  —  Horizontal  beds  of  shale-clay. 

For  in  this  case  the  depth  of  disintegration  of  the  shale  would 
depend  more  on  accidental  features,  such  as  the  existence  of 
joint  planes,  thinness  of  soil  cover,  etc. 


RESIDUAL  CLAYS  227 

An  interesting  and  somewhat  exceptional  case  of  the  formation 
of  a  high-grade  residual  clay  from  sandstone  has  recently  been 
noted  by  Loughlin.*  The  occurrence  is  at  West  Cornwall, 
Litchfield  County,  Connecticut,  where  a  highly  feldspathic  sand- 
stone has  decayed  in  place.  The  resulting  product  is  a  mixture 
of  quartz  grains  and  a  very  pure  residual  clay  or  "  kaolin."  Of 
course  the  material  requires  washing,  in  order  to  free  the  clay 
from  the  sand.  An  analysis  of  the  washed  product  gave  the 
following  results: 

Silica  (SiOa) 47.50 

Alumina  (A12O3) 37.40 

Iron  Oxide  (Fe2O3) 0.80 

Lime  (CaO) tr. 

Magnesia  (MgO) 0.00 

Alkalies  (K2O,  Na2O) 1.10 

Water 12.48 

Residual  from  Decay  of  Limestones.  —  The  formation  of  resid- 
ual clays  from  limestones  is  a  process  of  peculiar  interest,  not 
only  because  it  has  given  rise  to  many  large  clay  deposits,  but 
because  certain  factors  enter  into  the  question  which  are  absent 
from  the  decay  of  igneous  rocks  and  shales. 

Limestones  are  composed  f  essentially  of  lime  carbonate,  or  of 
a  mixture  of  lime  and  magnesium  carbonates.  Some  contain 
little  else  than  these  carbonates,  but  by  far  the  majority  of  lime- 
stones carry  appreciable  percentages  of  clayey  matter  (silica, 
alumina,  and  iron)  and  often  other  impurities  (sulphur,  alkalies, 
etc.).  Most  of  these  impurities  —  and  particularly  the  clayey 
materials  —  are  very  insoluble,  as  compared  to  lime  and  mag- 
nesium carbonates.  The  latter  are  readily  attacked  by  water 
carrying  dissolved  carbon  dioxide.  When  a  bed  of  limestone  is 
permeated  by  waters  so  charged,  the  carbonates  of  lime  and 
magnesia  are  carried  off  in  solution,  while  any  clayey  matter 
which  may  have  been  contained  in  the  limestone  is  left  behind. 
Long  exposure  to  such  action  will  result  in  the  removal  of  a  vast 
amount  of  limestone,  and  in  the  accumulation  of  a  great  thick- 
ness of  residual  material  (clay,  chert,  etc.),  as  a  mantle  over  the 
remnant  of  the  limestone,  even  when  the  original  limestone 

*  Clays  and  Clay  Industries  of  Connecticut,  pp.  15,  30,  31,  etc. 
t  For  a  more  detailed  discussion  of  the  composition  of  limestones,  reference 
should  be  made  to  pages  152-155. 


228 


BUILDING  STONES  AND  CLAYS 


contained  very  small  amounts  (1  to  3  per  cent)  of  such  clayey 
matter. 

An  example  may  make  the  case  clearer.     Suppose  that  a 
horizontal  bed  of  limestone  100  feet  thick,  whose  composition  is 

Per  cent. 

Silica 2£ 

Alumina 1| 

Iron  oxide 1 

Lime  carbonate 95 

(this  would  really  be  a  limestone  above  the  average  in  purity), 
were  attacked  by  percolating  water,  charged  with  carbon  dioxide, 

Original  surface 


]-— -  Thickness  of 

I     Limestone 
'  Removed  Jt»y 
Solution 


Residual  Clay- 
Limestone 


Fig.  28.  — Formation  of  residual  clay  from  limestone. 

the  lime  carbonate  would  be  removed  in  solution,  while  the  insol- 
uble matter  would  be  left  behind.  In  place  of  the  original  100- 
foot  bed  of  limestone,  there  would  remain  a  5-foot  bed  of  clay 
of  approximately  the  composition,  silica  50  per  cent,  alumina  30 
per  cent,  iron  oxide  20  per  cent.  Now  in  many  cases  the  con- 
ditions have  been  even  more  favorable  to  clay  formation  than  in 
the  case  supposed,  for  the  original  limestones  have  been  both 
thicker  and  more  impure. 


Chalk 


Fig.  29.  — Residual  clays  from  chalk. 


The  effect  of  such  weathering  on  an  inclined  series  of  chalky 
limestones  is  shown  in  Fig.  27. 


RESIDUAL  CLAYS 


229 


Another  excellent  example  of  a  deposit  of  clay  residual  from 
limestone  is  illustrated  in  Fig.  28.  This  shows  a  section  across 
such  a  deposit  at  Bertha,  Va.  The  blocked  area  in  the  section 
is  limestone,  containing  only  a  very  small  percentage  of  clayey 
matter.  By  its  solution,  however,  a  very  great  thickness  of 
residual  clay  is  accumulated,  and  this  caps  the  remaining  lime- 
stone as  shown  in  the  figure.  A  point  of  particular  interest  is 


Surface 


Fig.  30.  —  Residual  clays  from  limestone. 

the  very  irregular  form  of  the  base  or  floor  of  the  clay  deposit. 
It  will  be  seen  that  the  limestone  has  been  dissolved  so  irregu- 
larly as  to  leave  pillars  and  bosses  projecting  upward  into  the 
clay.  Such  a  deposit  must  of  necessity  be  drilled  very  carefully 
in  order  to  determine  the  available  tonnage.  Another  point 
brought  out  by  the  figures  is  the  sharpness  of  the  transition  from 
clay  to  unaltered  limestone.  The  whole  process  is  one  of  solu- 
tion, so  that  clays  residual  from  limestone  do  not  show  the 
gradual  change  downward  into  the  parent  rock  which  is  charac- 
teristic of  clays  residual  from  igneous  rocks  or  from  shale. 

Clays  derived  from  the  decay  of  limestones  are  commonly 
very  fine-grained,  and  consequently  very  fat  or  plastic.  The 
clay  itself  is  apt  to  be  rather  low  in  silica;  but  the  clay  deposit 
frequently  contains  nodules  of  chert  or  flint,  or  masses  (large  or 
small)  of  iron  pyrite  or  brown  iron  ore.  These  materials  are  as 
insoluble  as  the  clay,  and  like  it  are  left  behind  when  the  lime- 
stone is  dissolved.  On  the  other  hand,  the  limestone  clays  do 
not  ordinarily  contain  sand,  gravel,  or  pebbles. 

A  typical  series  of  such  clays  is  presented  below  in  Table  109, 
which  may  be  profitably  compared  with  the  analyses  already 
given  in  Table  108. 


230 


BUILDING  STONES  AND  CLAYS 


TABLE   109.  —  ANALYSES  OF  CLAYS  RESIDUAL  FROM 
LIMESTONE. 


l. 

2. 

3o. 

36. 

Silica  (SiO2)  

55  42 

43  37 

0  42 

48  96 

Alumina  (Al2Os) 

22  17 

25  07 

0  22 

26  27 

Iron  oxide  (Fe2O3) 

8  30 

15  16 

0  19 

10  53 

Lime  (CaO) 

0  15 

0  63 

29  77 

0  24 

Magnesia  (MgO)          .... 

1  45 

0  03 

20  69 

1  02 

Alkalies  (K2O,  Na2O)  

2  49 

3.70 

0.80 

n.d. 

Carbon  dioxide  (CO2) 

44  43 

n  d 

Water  ,  

9.86 

12.98 

3.41 

9.47 

1.  Morrisyille    Calhoun  County,  Ala.  l 

2.  Lexington,  Va.  ) 

??'  Limestone      I    Austinville,  Va.;  Bull.  No.  1,  Va.  Geol.  Sur.,  p.  98. 
36.   Residual  clay  ) 


CHAPTER  XV. 
TRANSPORTED   CLAYS. 

Origin  of  Transported  Clays.  —  The  transported  clays  differ 
from  the  residual  clays  principally  in  having  been  moved  from 
the  locality  at  which  they  were  formed,  so  that  their  point  of 
deposit  may  be  far  from  their  point  of  origin.  This  transpor- 
tation may  have  been  effected  through  the  agency  of  running 
water,  of  glacial  ice,  or  of  the  wind.  The  first  of  these  agents, 
however,  is  by  far  the  most  common  transporting  power;  ice 
has  moved  very  few  clays,  while  the  effect  of  wind  is  in  reality 
a  very  open  question. 

WATER-BORNE    OR    SEDIMENTARY    CLAYS. 

According  to  their  point  of  deposition  the  sedimentary  clays 
are  subdivided  into  stream,  lake,  and  marine. 

Marine  Clays.  —  The  material  carried  by  streams  and  rivers 
to  the  ocean  is  spread  out  finally  in  estuaries,  in  marshes  along  the 
coast  line,  or  as  a  mantle  over  the  ocean  depths.  In  all  these 
cases  the  finer  material  is,  of  course,  carried  the  farthest,  and  is 
deposited  only  at  points  where  the  force  of  the  transporting 
current  is  checked. 

No  very  sharp  line  can  be  drawn  between  certain  classes  of 
marine  and  stream  clays,  for  clays  deposited  in  the  delta  of  a 
river,  in  a  broad,  shallow  estuary  or  bay,  or  in  marshes  along 
the  coast  could  with  much  reason  be  considered  fresh-water 
rather  than  marine,  though  in  the  present  volume  they  are  for 
convenience  included  with  the  true  marine  clays. 

Marine  Clays  Proper.  —  Most  of  the  marine  clays  which  are 
forming  at  the  present  day  are,  of  course,  unavailable  for  com- 
mercial uses,  for  they  are  mostly  covered  by  the  waters  of  the 
ocean.  But  marine  clays  formed  during  earlier  geologic  periods 
are  of  great  importance,  for  earth  movements  have  often  elevated 
the  ocean  basins  or  ocean  shores  so  that  many  marine  sediments 
are  now  exposed  at  the  earth's  surface.  Owing  to  long-continued 

231 


232 


BUILDING  STONES  AND  CLAYS 


exposure  to  heat  and  pressure  of  the  clays  so  elevated,  the  older 
ones  have  generally  become  hardened  so  that  they  now  appear 
in  the  form  of  shales  or  slates,  rather  than  as  ordinary  soft  plastic 
clays.  The  more  recently  elevated  marine  clays,  however,  still 
retain  their  softness  and  plasticity,  as  is  notable  in  the  clay  de- 
posits of  the  coastal  plain. 

TABLE  110.  —  ANALYSES  OF  MARINE  CLAYS. 


«. 

2. 

3. 

Silica  (SiO2) 

62  80 

62  33 

61  59 

Alumina  (A12O3)*. 

18  23 

18  49 

19  10 

Iron  oxide  (Fe2O3,  FeO) 

6  40 

6  91 

7  53 

Lime  (CaO)  ... 

0  88 

1  00 

1  68 

Magnesia  (MgO)  

1  58 

1  53 

1  87 

Potash  (K2O)  

3  05 

2  41 

n  d 

Soda  (Na2O)  

1.48 

2  38 

n  d. 

Combined  water 

4  39 

3  81  [ 

Moisture 

1  31 

1  11  i 

5.51 

*  Including  small  percentages  of  titanic  oxide  (TiO2). 

1.  Thomaston,  Me.         ^ 

2.  Hayden's  Ft.,  South  SW.  T.  Schaller,  analyst. 

Thomaston,  Me.      ) 

3.  Rockland,  Me. 


Shales.  —  It  has  been  noted  previously  that  shales  are  simply 
clays  which  have  been  hardened  by  pressure.  This  statement, 
while  approximately  correct,  requires  some  restriction  for  our 
present  purposes.  For  shales  have  been  derived  almost  entirely 
from  extensive  deposits  of  clays  of  marine  origin  —  deposited 
along  seacoasts  or  in  large  basins  —  and  such  marine  deposits 
will  naturally  differ  considerably  from  glacial,  stream,  or  lake 
clays.  The  marine  clays  have,  in  general,  been  transported 
further  than  the  other  types  of  clay,  and  have  been  more  effec- 
tively sorted  while  in  transit.  For  this  reason  the  shales  derived 
from  them  rarely  show  the  same  irregularities  in  physical  com- 
position that  some  modern  clays  exhibit.  Shales,  for  example, 
are  rarely  so  full  of  coarse  sand,  gravel,  limestone  fragments,  etc., 
as  are  the  glacial  clays  of  the  northern  states.  Sandy  shales 
and  limy  shales  do  occur,  it  is  true,  but  even  in  this  case  such 
impurities  are  usually  more  regularly  distributed  throughout 
the  mass  of  the  rock  than  is  the  case  with  the  impurities  of  the 
glacial  clays. 


TRANSPORTED  CLAYS  233 

The  limy  shales  are  almost  exclusively  shales  which  occur 
interbedded,  in  comparatively  thin  layers,  with  limestones. 
Occasionally  a  limy  shale  will  owe  its  content  of  lime  almost 
entirely  to  the  fossil  shell  it  contains,  the  remainder  of  the  shale 
being  practically  free  from  carbonates.  For  both  of  the  above 
reasons  limy  shales  are  apt  to  be  a  source  of  trouble  in  the 
practical  working  of  a  plant  and  require  considerable  care  in 
quarry  management  to  insure  that  the  raw  materials  are  any- 
where near  uniform  in  composition  from  day  to  day. 

Slates.  —  Slates  *  are  clays  or  shales  which  have  been  so  hard- 
ened and  otherwise  affected  by  pressure  as  to  have  taken  on  a 
regular  parallel  cleavage,  being  thus  capable  of  being  readily 
split  into  thin  tough  plates.  The  origin,  composition,  and  dis- 
tribution of  slates  have  been  discussed  in  detail  elsewhere  in 
this  volume  (Chapter  VII).  Their  interest  in  the  present  con- 
nection is  due  to  the  fact  that  large  quantities  of  waste  slate  are 
produced  in  the  operations  of  quarrying  and  dressing  roofing  or 
mill  slate,  and  that  much  of  this  waste  could  be  utilized  in  the 
manufacture  of  clay  products. 

Stream  Clays.  —  A  stream  carrying  sediments  will  deposit  a 
portion  of  its  load  at  points  where  its  current  is  checked.  This 
is  likely  to  occur  in  the  broader  and  shallower  reaches  of  its 
course,  and  is  particularly  frequent  when  floods  have  caused  the 
stream  to  overflow  its  banks. 
In  this  last  case  the  sediment 
is  deposited,  levee  fashion,  par- 
allel to  the  course  of  the  stream. 

In  dealing  with  the  clays  de- 
posited along  the  larger  streams, 
it  will  frequently  be  found  that  pjg  31.  — Clay  terraces, 

they  occur  in  the  form  of  district 

terraces,  or  flat-topped  benches,  and  that  often  there  will  be 
several  pairs  of  such  terraces,  each  at  a  different  elevation.  Any 
one  of  several  causes  may  have  produced  this  arrangement,  but 
the  frequency  of  the  arrangement  itself  is  worth  bearing  in  mind. 

*  It  may  here  be  noted  that  geologists  restrict  the  term  slate  to  clay  rocks 
in  which  the  cleavage  has  been  developed  at  some  angle  to  the  original  bedding 
planes.  In  common  use,  however,  any  shale  which  breaks  into  flat  and  fairly 
even  plates  is  called  a  slate,  regardless  of  the  direction  of  the  faces  of  these 
plates. 


234 


BUILDING  STONES  AND   CLAYS 


A  very  typical  set  of  terrace-clay  deposits  is  shown  in  Fig.  32, 
reprinted  from  the  paper  by  Jones  later  cited  (page  252).  The 
deposits  shown  in  this  figure  are  those  occurring  along  the  Hudson 
River  at  many  points  on  both  of  its  banks,  though  in  the  figure 
only  a  few  deposits  on  the  east  bank  are  presented. 

TABLE  111.  — ANALYSES  OF  STREAM  CLAYS. 


Silica 
(SiO,). 

Alumina      IJS,°??de8 
(AW),).         (FF^ 

Lime 
(CaO). 

Mag- 
nesia 
(MgO). 

Potash 
(K2O). 

Soda 
(NajO) 

Carbon     Corn- 
dioxide     bined 
(CO2).     water. 

1 

52.73 

22.25           7.69 

1.48 

3.20 

4.28 

2.22 

4.91 

2 

50.33 

27.06           4.91 

1.22 

3.34 

4.40 

1.78 

5.24 

3 

55.27 

20.52           6.89 

2.21 

2.80 

3.43 

2.82 

5.06 

4 

51.10 

17.65           6.47 

7.45 

0.87 

n.d. 

n.d. 

n.d.      n.d. 

5 

50.60 

21.00           7.35 

3.75 

0.96 

n.d. 

n.d. 

n.d.      n.d. 

6 

59.81 

22.00 

4.35 

2.29 

n.d. 

n.d. 

n.d.      7.89 

1.  South  Windsor,  Conn, 

2.  West  Hartford,  Conn. 

3.  Newfield,  Conn. 

4.  Coeyman's  Landing,  N.  Y. 

5.  Catskill,  N.  Y. 

6.  Barrytown,  N.  Y. 


W.  T.  Schaller,  analyst;  Bull.  4,  Conn.  Geol. 
Sur.,  p.  59. 


Bull.  35,  N.  Y.  State  Museum. 


p.  705. 
p.  702. 
p.  702. 


Lake  Clays.  —  Streams  flowing  into  lakes  or  ponds  tend  to 
deposit  their  sediment  at  the  point  where  their  flow  is  checked. 
In  small  lakes,  therefore,  the  heavier  sediments  are  commonly 
deposited  where  the  stream  enters  the  lake,  while  the  drier  clayey 
deposits  occur  a  little  further  off  shore. 

In  lakes  large  enough  to  be  seriously  affected  by  wind  and 
current  action,  the  distribution  and  character  of  the  clay  deposits 
are  closely  similar  to  those  of  marine  clays. 

Ice-borne  or  Glacial  Clays.  —  The  finer  material  transported 
by  glacial  ice,  and  deposited  along  or  near  the  margin  of  the  gla- 
cier, often  forms  clay  deposits  of  commercial  importance.  Owing 
to  the  purely  mechanical  origin  of  clays  of  this  type,  they  com- 
monly contain  fragments  of  limestone,  sand,  pebbles,  etc.,  which 
limit  their  use  to  the  manufacture  of  low-grade  products. 

Wind-borne  or  Eolian  Clays.  —  Many  geologists  consider  that 
the  vast  deposits  of  loess  which  border  the  Mississippi  and  other 
great  rivers  are  of  eolian  origin,  the  material  having  been  trans- 
ported by  the  wind. 


Brockway 


W.E.  Verplanck 


o 


E.I.  E.2.         E.3.  E.4.          £.5. 


E.l.          E.2.  £.3.  E.4.          £.5. 


Legend 
taml 

tyZft.  Yellow  Clay 
g^3  Blue  Clay 

Om  Blue  Clay  &  Quick  Sand 

^_.   __^ 
l^a  Rock  W.2 

s,j  Horizontal,  1=685  ft. 
(Vertical.       1  =  137  ft. 

Fig.  32.  —  Clay  terraces  along  Hudson  River.     (C.  C.  Jones.)  [235] 


. 
|  E.l.          £.2.  E.8.  E.4.  E.5. 


236 


BUILDING  STONES  AND  CLAYS 


The  loess  clays  from  various  points  along  the  Mississippi  are 
strikingly  uniform  in  composition,  the  range  of  the  principal 
elements  being  slight.  The  following  series  of  analyses  illustrate 
this  point. 

TABLE  112.  —  ANALYSES  OF  LOESS  CLAYS. 


I. 

2. 

3. 

4. 

5. 

6. 

Silica  (SiO2)  .  . 

72  00 

71  11 

74  39 

73  80 

73  92 

67  92 

Alumina  (AUOs)  

11  97 

11  62 

12  03 

13  19 

11  65 

11  76 

Iron  oxide  (Fe2O3)  

3  51 

3  90 

4  06 

3  43 

4  74 

6  72 

Lime  (CaO) 

1  80 

2  37 

1  50 

0  86 

1  43 

1  63 

Magnesia  (MgO)  

1.35 

1.47 

1  53 

0  68 

0  60 

1  18 

Alkalies  (K2O,  Na2O) 

3  25 

3  14 

3  01 

2  94 

3  13 

3  79 

Combined  water  .  . 

6  42 

6  71 

3  17 

5  26 

3  08 

5  36 

Specific  gravity  

2.17 

2.20 

2.09 

2.17 

1.98 

1.  Kansas  City. 

2.  Boonville. 

3.  Jefferson  City. 


4.  Hannibal. 

5.  St.  Louis. 

6.  Gladbrook,  Iowa. 


List  of  References  on  Origin  of  Clays: 

Barus,  C.     On  the  thermal  effect  of  the  action  of  aqueous  vapor  on 

feldspathic  rocks  (kaolinization).     School  of  Mines  Quarterly,  vol. 

6,  pp.  1-24.     1885. 
Bulman,   G.  W.      Underclays:  a  preliminary  study.     Geol.  Mag.,  new 

series,  decade  III,  vol.  9,  pp.  351-361.     1892. 
Cook,  G.  H.       Report  on  the  clay  deposits  of  New  Jersey,  1878,  pp. 

267-306. 
Cushman,  A.  S.     On  the  cause  of  the  cementing  value  of  rock  powders 

and  the  plasticity  of  clays.     Jour.  Amer.  Chem.  Soc.,  vol.  25,  pp. 

451-468.     1903. 
Hopkins,  T.  C.       A  short  discussion  of  the  origin  of  the  coal  measures 

fire  clays.     Amer.  Geol.,  vol.  28,  pp.  47-51.     1901. 
Hopkins,  T.  C.     Fire  clays  of  the  coal  measures.     Mines  and  Minerals, 

vol.  22,  p.  596.     1902. 
Hopkins,  T.  C.     Kaolin:  its  occurrence,  technology,  and  trade.     Min. 

Ind.,  vol.  7,  pp.  148-160.     1899. 
Hutchings,  W.  M.     Further  notes  on  fire  clays,  etc.     Geol.  Mag.,  new 

series,  decade  III,  vol.  8,  pp.  164-169.     1891. 
Hutchings,  W.  M.     Rutile  in  fire  clays.     Geol.  Mag.,  new  series,  decade 

III,  vol.  8,  pp.  304-306.     1891. 
Hutchings,  W.  M.     Notes  on  sediments  dredged  from  the  English  lakes. 

Geol.  Mag.,  new  series,  decade  IV,  vol.  1,  pp.  300-302.     1894. 
Irving,  R.     Kaolin  in  Wisconsin.     Trans.  Wis.  Acad.  of  Sci.,  vol.  3,  pp. 

3-30.    1876. 


TRANSPORTED  CLAYS  237 

Johnson,  S.  W.,  and  Blake,  J.  M.     On  kaolinite  and  pholerite.     Amer. 

Jour,  of  Sci.,  vol.  43,  p.  351.     1876. 
Merrill,  G.  P.     A  Treatise  on  Rocks,  Rock-Weathering,  and  Soils,  8vo, 

411  pages,  Macmillan  &  Co.,  New  York.     1897. 
Merrill,  G.  P.     What  constitutes  a  clay.     Amer.  Geol.,  vol.  30,  pp.  318- 

322.     1902. 
Orton,  E.     The  clays  of  Ohio,  their  origin,  composition,  and  varieties. 

Rep.  Ohio  Geol.  Sur.,  vol.  7,  pp.  45-68.     1893. 

Ries,  H.     The  origin  of  kaolin.     Trans.  Amer.  Ceramic  Soc.,  vol.  2.     1900. 
Wheeler,  H.  A.     Clay  deposits  of  Missouri.     Rep.  Missouri  Geol.  Sur., 

vol.  11,  pp.  17-27,  49-114.     1896. 


CHAPTER   XVI. 
DISTRIBUTION   OF   CLAYS. 

Geographic  Distribution  of  Clays.  —  In  a  volume  of  this  size 
little  of  value  can  be  said  concerning  the  local  distribution  of 
clays,  but  a  few  general  statements  will  be  made  which  may 
serve  as  a  guide  to  exploration  or  to  further  study  of  the  matter. 
Certain  large  areas  can  at  least  be  roughly  defined,  within  each 
of  which  areas  a  certain  class  of  clay  predominates.  If  the 
reader  desires  details  regarding  the  distribution  of  clays  in  any 
particular  state,  or  smaller  area,  reference  should  of  course  be 
made  to  the  reports  listed  on  pages  24Q-243. 

The  glaciated  area  lies  to  the  north  of  the  line  which  marks 
the  extreme  southern  limit  attained  by  the  great  Nice  sheets. 
North  of  this  line  the  bedrock  was  swept  clear  of  all  its  over- 
lying de*bris  by  the  glaciers,  and  except  in  a  few  instances  no 
large  amount  of  postglacial  decay  has  occurred.  Residual  clays 
are  therefore  practically  lacking  in  the  glaciated  area. 

The  coastal  plain  is  the  term  applied  by  geologists  and  physiog- 
raphers to  the  great  belt  of  lowland  that,  from  New  York  City 
southward,  borders  the  Atlantic  and  Gulf  coasts.  Its  eastern 
and  southern  limits  are,  of  course,  the  shores  of  the  Atlantic 
and  the  Gulf  of  Mexico.  Its  western  and  northern  limits  may 
be  located  closely  by  tracing  a  line  from  New  York  City  through 
Trenton,  Philadelphia,  Baltimore,  and  Washington. 

The  clays  of  the  coastal  plain  are  mostly  of  marine  origin, 
having  been  deposited  at  a  time  when  the  coast  line  was  just 
inland  of  their  present  location.  They  are  therefore  more  widely 
distributed  than  glacial  or  stream  clays  and  their  general  char- 
acter and  location  can  usually  be  predicted,  with  some  certainty, 
in  advance  of  actual  exploration. 

The  coastal  plain  clays  are  usually  quite  siliceous,  and  low  in 
lime,  magnesia,  and  alkalies.  They  furnish  pottery,  stoneware, 
and  firebrick  clays,  the  pottery  clays  of  New  Jersey  and  the 

238 


DISTRIBUTION   OF  CLAYS 


239 


Fl  -2 

11 


'i 


D 


240  BUILDING  STONES  AND   CLAYS 

stoneware  clays  of  northern  Mississippi  and  western  Tennessee 
and  Kentucky  being  worthy  of  special  note. 

In  the  elevated  Piedmont  and  Appalachian  regions  which  lie 
inland  of  the  Coastal  Plain,  the  decay  of  igneous  and  meta- 
morphic  rocks  has  given  rise  to  bodies  of  residual  clays.  These 
differ  in  size  and  grade  according  to  the  rocks  from  which  they 
are  derived. 

The  region  northwest  of  the  Blue  Ridge  (and  its  northern  and 
southern  continuations)  is  covered  by  old  sedimentary  rocks  — 
sandstones,  limestones,  and  shales.  Here  again  a  distinction  is 
to  be  made  between  the  regions  north  and  south  of  the  glacial 
border. 

In  the  great  Appalachian  Valley  which  parallels  the  western 
flank  of  the  Blue  Ridge  or  Appalachian  range,  deep  weathering 
of  limestone  and  shale  beds  has  given  rise  to  heavy  deposits  of 
residual  clay,  particularly  south  of  the  glacial  limit. 

The  plateau  west  of  the  Great  Valley  yields  chiefly  shales, 
varying  widely  in  their  character  and  commercial  value. 

List  of  References  on  the  Distribution  of  Clays  and  Shales.  — 
The  literature  of  clays  is  so  extensive  that  the  descriptive  papers 
in  the  following  list  have  been  arranged  by  States  in  alphabetical 
order. 

General  United  States: 

Ries,  H.     The  clays  of  the  United  States  east  of  the  Mississippi  River. 

Professional  Paper  No.  11,  U.  S.  Geol.  Sur.,  289  pp.     1903. 
Alabama: 

Ries,  H.,  and  Smith,  E.     Preliminary  report  on  the  clays  of  Alabama. 

Bull.  6,  Ala.  Geol.  Sur.,  220  pp.     1900. 
Arkansas: 

Branner,  J.  C.     The  cement  materials  of  southwest  Arkansas.     Trans. 

Am.  Inst.  Min.  Engrs.,  vol.  27,  pp.  42-63. 
Branner,  J.  C.     The  clays  of  Arkansas.      Bull.  No.  — ,  U.  S.  Geol.  Sur. 

(In  press.) 
California: 

Johnson,  W.  D.     Clays  of  California.     9th  Ann.  Rep.  Cal.  State  Min., 

pp.  287-308.     1890. 
Ries,  H.     The  clay- working  industry  of  the  Pacific  Coast  States.     Mines 

and  Minerals,  vol.  20,  pp.  487-488.     1900. 
Colorado: 

Lakes,  A.     Gypsum  and  clay  in  Colorado.     Mines  and  Minerals,  vol.  20. 

December,  1899. 

Ries,  H.     The  clays  and  clay-working  industry  of  Colorado.     Trans. 
Am.  Inst.  Min.  Engrs.,  vol.  27,  pp.  336-340.     1898. 


DISTRIBUTION  OF  CLAYS  241 

Florida: 

Memminger,  C.  J.     Florida  \kaolin  deposits.     Eng.  and  Min.  Jour.,  vol. 

57,  436  pp.     1894. 

Vaughan,  T.  W.  Fuller's  earth  deposits  of  Florida  and  Georgia.  Bull. 
213,  U.  S.  Geol.  Sur.,  pp.  392-399.  1903. 

Georgia: 

Ladd,  G.  E.     Preliminary  report  on  a  part  of  the  clays  of  Georgia.     Bull, 

6A,  Ga.  Geol.  Sur.,  204  pp.     1898. 
Vaughan,  T.  W.     Fuller's  earth  deposits  of  Florida  and  Georgia.     Bull. 

213,  U.  S.  Geol.  Sur.,  pp.  392-399. 

Indiana: 

Blatchley,  W.  S.  A  preliminary  report  on  the  clays  and  clay  industries 
of  the  coal-bearing  counties  of  Indiana.  20th  Ann.  Rep.  Ind.  Dept. 
Geol.  and  Nat.  Res.,  pp.  24-187.  1896. 

Blatchley,  W.  S.     Clays  and  clay  industries  of  northwestern  Indiana. 
22d  Ann.  Rep.  Ind.  Dept.  Geol.  and  Nat.  Res.,  pp.  105-153.     1898. 
Iowa: 

Beyer,  S.  W.,  and  others.  Clays  and  clay  industries  of  Iowa.  Vol.  14, 
Rep.  Iowa  Geol.  Sur.,  pp.  27-643.  1904. 

Kansas: 

Prosser,  C.  S.     Clay  deposits  of  Kansas.     Min.  Res.  U.  S.  for  1892, 

pp.  731-733.     1894. 
Kentucky: 

Crump,  H.  M.     The  clays  and  building  stones  of  Kentucky.     Eng.  and 

Min.  Jour.,  vol.  66,  pp.  190,  191.     1898. 
Louisiana: 

Clendennin,  W.  W.     Clays  of  Louisiana.     Eng.  and  Min.  Jour.,  vol.  66, 

pp.  456,  457.     1898. 
Ries,  H.     Report  on  Louisiana  clay  samples.     Rep.  La.  Geol.  Sur.  for 

1899,  pp.  263,  275.     1900. 
Maryland: 

Ries,  H.     Report  on  the  clays  of  Maryland.     Rep.  Md.  Geol.  Sur.,  vol.  4, 

pt.  3,  pp.  203-507,  1902. 
Massachusetts : 

Whittle,  C.  L.     The  clays  and  clay  industries  of  Massachusetts.     Eng. 

and  Min.  Jour.,  vol.  66,  pp.  245,  246,  1898. 
Michigan: 

Ries,  H.  Clays  and  shales  of  Michigan.  Rep.  Mich.  Geol.  Sur.,  vol.  8, 
pt.  1,  67  pp.  1900. 

Minnesota: 

Berkey,  C.  P.     Origin  and  distribution  of  Minnesota  clays.     Am.  Geol., 

vol.  29,  pp.  171-177.     1902. 
Mississippi: 

Crider,  A.  F.     Clays  of  Mississippi.     Bull.  1,  Miss.  Geol.  Surv. 
Eckel,  E.  C.     Stoneware  and  brick  clays  of  western  Tennessee  and  north- 
western Mississippi.     Bull.  213,  U.  S.  Geol.  Sur.,  pp.  382-391.    1903. 


242  BUILDING  STONES  AND  CLAYS 

Missouri: 

Wheeler,  H.  A.    Clay  deposits  of  Missouri.     Rep.  Mo.  Geol.  Sur.,  vol.  2, 

622  pp.    1896. 
Montana: 

Rowe,  J.  P.     The  Montana  clay  industry.     Brick,  vol.  24,  pp.  1-3. 

Jan.,  1906. 
Nebraska: 

Gould,  C.  N.,  and  Fisher,  C.  A.     The  Dakota  and  Carboniferous  clays 
of  Nebraska.     Ann.  Rep.  for  1900,  Neb.  Bd.  of  Agric.,  pp.  185-194. 
1901. 
New  Jersey: 

Cook,  G.  H.,  and  Smock,  J.  C.     Report  on  the  clay  deposits  of  New 

Jersey.     N.  J.  £eol.  Sur.,  381  pp.     1878. 

Ries,  H.,  Kiimmel,  B.,  and  Knapp,  G.  N.     The  clays  and  clay  industries 
of  New  Jersey.     Final  Rep.  State  Geol.,  N.  J.,  8vo.,  vol.  6,  548  pp. 
1904. 
New  York: 

Jones,  C.  C.  A  geologic  and  economic  survey  of  the  clay  deposits  of 
the  lower  Hudson  River  Valley.  Trans.  Am.  Inst.  Min.  Engrs., 
vol.  29,  pp.  40-83.  1900. 

Ries,  H.  Clays  of  New  York.  Bull.  35,  N.  Y.  State  Museum,  455  pp. 
1900. 

North  Carolina: 

Holmes,  J.  A.     Notes  on  the  kaolin  and  clay  deposits  of  North  Carolina. 

Trans.  Am.  Inst.  Min.  Engrs.,  vol.  25,  pp.  929-936.     1896. 
Ries,  H.     Clay  deposits  and  clay  industry  in  North  Carolina.     Bull.  13, 

N.  C.  Geol.  Sur.,  157  pp.    1897. 
North  Dakota: 

Babcock,  E.  J.     Clays  of  economic  value  in  North  Dakota.     1st  Rep. 

N.  D.  Geol.  Sur.,  pp.  27-55.     1901. 
Ohio: 

Orion,  E.     The  clays  of  Ohio  and  the  industries  established  upon  them. 

Rep.  Ohio  Geol.  Sur.,  vol.  5,  pp.  643-721.     1884. 
Orton,  E.     The  clays  of  Ohio:  their  origin,  composition,  and  varieties. 

Rep.  Ohio  Geol.  Sur.,  vol.  7,  pp.  45-68.     1893. 
I    Oregon: 

Ries,  H.     The  clay-working  industries  of  the  Pacific  Coast  states.    Mines 

and  Minerals,  vol.  20,  pp.  487-488.     1900. 
Pennsylvania : 

Hopkins,   T.   C.     Clays  of  western  Pennsylvania.     Appendix  to  Ann. 

Rep.  Pa.  State  Coll.  for  1897-98,  184  pp.     1898. 
Hopkins,    T.    C.     Clays   of   southeastern   Pennsylvania.     Appendix   to 

Ann.  Rep.  Pa.  State  Coll.  for  1898-99,  76  pp.     1899. 
Hopkins,  T.  C.     Clays  of  the  Great  Valley  and  South  Mountain  areas. 

Appendix  to  Ann.  Rep.  Pa.  State  Coll.  for  1899-1900,  45  pp.     1900. 
Woolsey,  L.  H.     Clays  of  the  Ohio  Valley  in  Pennsylvania.     Bull.  225, 

U.  S.  Geol.  Sur.,  pp.  463-480.     1904. 


DISTRIBUTION  OF  CLAYS  243 

South  Carolina: 

Sloan,  E.    A  preliminary  report  on  the  clays  of  South  Carolina.     Bull.  1, 

S.  C.  Geol.  Sur.,  171  pp.     1904. 
South  Dakota: 

Todd,  J.  E.    The  clay  and  stone  resources  of  South  Dakota.     Eng.  and 

Min.  Jour.,  vol.  66,  pp.  371.     1898. 
Tennessee: 

Eckel,  E.   C.     Stoneware  and  brick  clays  of  western  Tennessee  and 
northwestern  Mississippi.     Bull.  213,  U.  S.  Geol.  Sur.,  pp.  382-391. 
1903. 
Texas: 

Kennedy,  W.     Texas  clays  and  their  origin.     Science,  vol.  22,  pp.  297- 

300.     1893. 
Washington: 

Landes,  H.     Clays  of  Washington.     Rep.  Washington  Geol.  Sur.,  vol.  1, 

pt.  2,  pp.  13-23.     1902. 
Wisconsin: 

Buckley,  E.  R.     The  clays  and  clay  industries  of  Wisconsin.     Bull.  7, 

Wis.  Geol.  Sur.,  304  pp.     1901. 
Irving,  R.     Kaolin  in  Wisconsin.     Trans.  Wis.  Acad.  Sci.,  vol.  3,  pp.  3- 

30.     1876. 
Wyoming: 

Knight,  W.  C.     The  building  stones  and  clays  of  Wyoming.     Eng.  and 
Min.  Jour.,  vol.  66,  pp.  546,  547.     1898. 


CHAPTER  XVII. 
FIELD   EXAMINATION   OF   CLAY  DEPOSITS. 

THE  data  obtained  in  the  course  of  a  field  examination  should 
cover  the  amount  of  clay  present,  its  character  from  a  techno- 
logic point  of  view,  and  such  other  features  (drainage,  stripping, 
transportation)  as  will  affect  the  commercial  value^of  the  deposit. 
These  field  data  will  of  course  have  to  be  supplemented]  by  lab- 
oratory tests  on  the  samples  obtained. 

The  engineer  called  upon  to  examine  and  report  upon  a  clay 
property  will  do  well  to  realize  that  the  problem  before  him  is 
one  which  properly  falls  largely  within  the  domain  of  applied 
geology.  The  form  and  extent  of  the  clay  deposits  are,  it  is 
true,  determined  by  engineering  means,  but  the  proper  inter- 
pretation of  the  data  afforded  by  the  pits,  trenches,  or  drill  holes 
will  usually  require  a  working  knowledge  of  general  geologic 
principles.  These  principles  are  not  difficult  to  understand,  nor 
are  they  hard  to  apply. 

The  subject  of  field  examination  might  naturally  be  divided 
into  two  parts:  (1)  the  purely  mechanical  portion,  relating  to 
methods  of  drilling,  boring,  etc.,  and  (2)  the  geologic  portion, 
relating  to  the  interpretation  of  the  data  so  obtained,  for  this  is 
the  order  in  which  any  particular  piece  of  work  would  be  taken 
up.  But  in  discussing  the  subject  it  is  more  convenient  to  almost 
reverse  this  arrangement,  by  describing  first  the  general  conduct 
of  the  work,  and  then  taking  up  the  methods  of  getting  the  data. 

THE  GENERAL  CONDUCT  OF  FIELD    WORK. 

The  Use  of  Geological  Reports.  —  Before  taking  the  field  it 
is  advisable  to  find  out  whether  or  not  geological  reports  on  the 
district  have  been  published.  The  federal  government  and 
most  states  support  geological  surveys,  and  in  many  cases  it  will 
be  found  that  these  organizations  have  published  more  or  less 
complete  reports  on  either  the  general  geology  or  the  clay  re- 

244 


FIELD  EXAMINATION  OF  CLAY  DEPOSITS  245 

sources  of  the  district  which  is  to  be  examined  in  detail  by  the 
engineer.  Many  such  reports  are  listed  on  pages  240-243  of  this 
volume. 

The  help  to  be  gained  from  these  geological  reports  will  depend 
largely  on  the  state  in  which  the  deposit  is  located. 

Very  detailed  and  generally  satisfactory  reports  on  clays  have 
been  issued  by  the  states  of  Alabama,  Connecticut,  Indiana, 
Iowa,  Maryland,  Michigan,  Missouri,  New  Jersey,  New  York, 
North  Carolina,  Ohio,  South  Carolina,  and  Wisconsin.  Partial 
or  otherwise  incomplete  reports  have  been  issued  for  Georgia, 
Mississippi,  North  Dakota,  Pennsylvania,  South  Dakota,  and 
Washington.  Scattered  data  of  some  value  are  on  record  for 
Arkansas,  California,  Florida,  Kansas,  Kentucky,  Louisiana, 
and  other  states.  Detailed  reports  on  part  or  all  of  the  clays 
of  Arkansas,  Illinois,  Virginia,  and  Texas  are  known  to  be  in 
preparation  at  the  date  of  writing. 

These  reports  vary  greatly  in  their  detail  and  value.  Even  the 
poorest  of  these  reports,  however,  will  contain  information  that 
will  save  needless  labor. 

Effect  of  Kind  of  Clay  on  Methods  of  Work.  —  The  material 
to  be  reported  on  may  be  (1)  a  hard  shale,  even  on  its  outcrop; 
(2)  a  shale  which  has  weathered  so 
as  to  appear  soft  and  claylike;  (3) 
an  ordinary  soft  plastic  clay,  or  (4) 
a  residual  "  kaolin  "  derived  from 
a    mass    or    dike    of    decomposed 
granite  or  feldspar.     Each  of  these 
types  will  present  different  problems,  and  may  require  different ' 
methods  of  field  work. 

The  importance  of  first  determining  the  method  of  origin  of 
the  deposit  lies  in  the  fact  that  it  influences  both  the  form  of  the 
deposit  and  the  character  of  the  material.  If  the  material  is 
merely  a  soft  surface  clay,  then  we  may  expect  to  find  a  flat- 
lying  and  basin-shaped  deposit,  and  our  only  interest  in  the 
hard  rocks  of  the  region  will  arise  from  the  fact  that  they  may 
form  the  lower  boundary  and  sides  of  the  deposit.  But  if  the 
material  is  a  shale,  the  dip  and  strike  of  other  beds  of  hard  rock 
will  probably  prove  of  interest,  for  we  may  fairly  expect  the 
shale  deposit  to  agree  in  these  particulars  with  adjacent  beds 
of  limestone,  sandstone,  etc. 


246  BUILDING  STONES  AND  CLAYS 

A  case  in  point  may  be  cited  in  which  the  owner  insisted 
that  the  ridge  in  which  the  clay  occurred  was  composed  entirely 
of  high-grade  clay  —  a  thickness  of  800  feet  or  more  being  claimed. 
The  statement  was  inherently  improbable,  owing  to  the  geologic 
structure  of  the  region,  but  the  property  was  visited.  A  large 
number  of  pits  had  been  run  in  on  clay  at  various  elevations  on 
both  flanks  of  the  ridge,  and  a  shallow  trench  had  been  cut 
transversely  across  the  top  of  the  ridge.  The  trench  and  all 
the  pits  showed  clay,  and  the  owner  pointed  to  this  triumph- 
antly as  proving  his  statement.  Outcrops  were  scarce,  as  both 
top  and  flanks  of  the  ridge  were  well  covered  with  soil  and  tim- 
ber, but  several  carefully  meas- 
ured sections,  made  at  various 
points,  when  combined  showed 
that  the  conditions  were  as  in 
Fig.  35.  In  place  of  a  solid 
bed  of  clay  800  feet  thick  there 
were  in  reality  a  number  of  clay 

Fig.  35.- Interbedded  sandstones  and  beds>    one    30    feet    thick    but 

shale-clays.  most  of  them   varying  from  4 

inches    to    3    feet  —  the    total 

thickness  of  all  the  clay  beds  was  not  over  60  feet,  and  the  remain- 
ing 770  feet  was  sandstone.  But  the  case  was  even  worse  than 
this.  In  looking  over  the  face  cut  into  the  30-foot  clay  bed, 
a  number  of  beds  of  loose  sand  were  noticed.  Careful  examina- 
tion showed  that  the  clays  were  really  the  exposed  weathered 
outcrops  of  a  series  of  shales,  that  the  sands  were  similarly 
weathered  sandstones,  and  that  consequently  when  the  workings 
were  driven  in  under  cover  the  owner  might  expect  to  find,  in 
place  of  the  30-foot  clay  bed  exposed  at  the  outcrop,  a  series 
of  shale  beds  interbedded  with  sandstones,  and  that  these  shales 
would  probably  contain  impurities  which  had  been  removed  by 
weathering  from  the  clays  which  showed  at  the  outcrop. 

Now  in  this  case  all  this  information  could  have  been  obtained 
directly,  but  only  at  prohibitive  expense,  by  deep  drilling  across 
the  ridge.  Handling  it  purely  as  an  engineering  problem  would 
have  required  several  months'  work  and  the  expenditure  of 
several  thousand  dollars,  while  by  the  application  of  purely 
geologic  methods  of  reasoning  and  field  work  the  same  results 
were  secured  in  less  than  a  day. 


FIELD  EXAMINATION  OF  CLAY  DEPOSITS  247 

Examination  of  Shale  Deposits.  —  Shales  are  mostly  of  marine 
origin,  and  were  deposited  in  extensive  water  areas.  Any  given 
bed  of  shale  is  therefore  apt  to  be  quite  regular  both  in  thickness 
and  in  composition,  for  considerable  distances.  This  materially 
lessens  the  labor  of  the  explorer.  If  on  visiting  a  property  he 
finds,  for  example,  a  good  outcrop  which  shows  a  30-foot  bed  of 
shale  underlain  by  a  bed  of  limestone  and  overlain  by  strata  of 
sandstone,  he  may  be  fairly  sure  that  this  shale  bed  will  probably 
not  vary  greatly  in  thickness  or  in  its  associated  rocks  within 
the  limits  of  the  property.  It  would  be  fair  to  expect  that  its 
thickness  will  not  fall  below  25  or  rise  above  35  feet  in  a  quarter 
mile.  It  would  also  be  a  reasonable  expectation  —  and  this  is 
a  matter  of  great  value  —  that  if  at  some  near-by  point  he  finds 
the  limestone  outcropping,  with  perhaps  a  soil-covered  slope 
above  it,  trenching  above  the  limestone  would  reveal  the  shale 
in  its  proper  position.  An  outcrop  of  the  overlying  sandstone, 
on  the  other  hand,  would  lead  the  engineer  to  trench  on  the 
slope  below  it  in  order  to  uncover  the  shale  bed. 

In  this  connection  it  is  well  to  recollect  that  in  most  of  the 
shale-producing  areas  of  the  United  States  the  rocks  are  lying 
in  an  almost  horizontal  attitude.  If  a  shale  bed  outcrops  in  the 
flank  of  a  ridge,  the  shale  is  apt  to  weather  so  as  to  produce  quite 
steep  but  regular  slopes,  usually  slippery  because  covered  with 
loose  fragments  of  shale.  Sandstone  or  heavy  limestone  beds, 
under  similar  conditions,  would  be  apt  to  form  very  marked 
terraces  or  stepped  slopes.  These  conditions  are  well  shown  in 
Fig.  25,  which  is  a  drawing  to  scale.  Here  a  sandstone  bed  forms 
the  crest  of  the  ridge,  a  limestone  bed  forming  a  very  marked 
terrace  about  one-third  of  the  way  down  the  slope,  while  the 
shale  beds  above  and  below  the  limestone  give  the  usual  shale 
type  of  topography.  These  facts  are  of  service  in  tracing  a  shale 
bed  throughout  a  property. 

Examination  of  Soft  Clay  Deposits.  —  The  principal  difference 
between  deposits  of  shales  and  of  soft  clays,  so  far  as  the  present 
connection  is  involved  is  (1)  that  shales  vary  little  in  thickness 
and  associated  rocks  as  compared  with  soft  clays;  and  (2)  that 
shale  beds  can  be  followed  down  under  overlying  rocks,  while 
most  beds  of  soft  clay  terminate  as  soon  as  hard  rock  is  struck 
either  in  the  bottom  or  the  sides  of  a  deposit.  The  only  promi- 
nent exceptions  to  this  rule  are  the  Cretaceous  and  Tertiary 


248  BUILDING  STONES  AND   CLAYS 

clays  of  the  coastal  plain  (see  pages  238,  239),  for  though  these 
are  soft  clays,  they  are  quite  regular  in  thickness  and  associated 
strata. 

In  dealing  with  deposits  of  soft  clays,  therefore,  greater  irregu- 
larity of  form  may  be  expected  than  when  shales  are  in  question, 
and  the  work  of  exploration  and  examination  must  be  carried 
on  with  accordingly  greater  care. 

The  forms  which  clay  deposits  may  take  are  infinite,  but  two 
general  types  may  be  expected  to  occur  more  frequently  than 
the  others.  These  are  the  bench  and  the  lens.  Clays  which  are 
deposited  along  stream  or  river  banks  usually  occur  in  the  first  of 
these  forms,  as  distinct  benches  or  terraces  (see  pages  233,  234, 
and  Figs.  31,  32) .  Clays  which  have  been  found  in  lakes  usually 
occur  in  the  second  form. 

Dealing  with  Known  Deposits.  —  If  the  area  occupied  by  the 
clay  deposit  is  small  and  fairly  well  known  in  advance,  it  will  be 

sufficient  to  lay  it  off  in  squares 
25,  50,  or  100  feet  on  a  side;  de- 
termine the  elevations  at  the  cor- 
ners of  these  squares,  and  then  drill 
or  sink  a  test  pit  at  each  corner. 
The  results  of  the  borings  or  pits 
are  then  to  be  plotted  so  as  to  give 
two  series  of  cross  sections  across 
Fig.  36.  — Basin  or  lens,  shaped  tne  deposit  at  right  angles  to  each 
clay  deposit.  other.  This  is  a  purely  mechanical 

performance,  and  little  except  care 

is  required  to  carry  it  out.  It  is  sufficient  only  in  dealing  with 
small  deposits,  or  when  the  general  form,  extent  and  character 
of  the  deposit  is  already  well  known.  Such  cases  will  arise  when 
a  brick  plant  acquires  property  adjacent  to  its  own  clay  pits, 
when  new  openings  are  to  be  run  in  on  a  well-known  "  vein  "  of 
fire  clay,  and  in  other  similar  circumstances. 

For  such  work  it  is  rarely  necessary  to  lay  off  the  squares  with 
a  transit  and  tape,  or  to  determine  altitudes  with  a  Y  level.  In 
many  cases  a  pocket  compass  and  pacing  will  suffice  to  give 
direction  and  distance,  while  a  Locke  level  can  be  used  for  eleva- 
tion. If  the  case  requires  more  refinement,  the  "  drainage  "  and 
"  architects'  "  levels  made  by  different  makers  are  sufficiently  pre- 
cise for  such  work  and  will  probably  be  the  best  instruments  to  use. 


FIELD   EXAMINATION  OF  CLAY  DEPOSITS  249 

METHODS  OF  BORING. 

The  earth  auger  is  usually  the  best  and  cheapest  instrument 
for  determining  the  thickness  of  clay  deposits  and  securing 
samples  of  the  clays  at  various  depths.  It  consists  of  an  auger 
attached  to  one  or  more  lengths  of  coupled  pipe,  the  upper  length 
of  pipe  being  provided  with  a  T  handle.  The  auger  is  sunk  by 
turning  the  handle,  and  on  withdrawing  it  a  sample  of  the  clay 
is  caught  on  the  auger  screw.  The  use  of  this  implement  is 
limited  to  the  clays  proper  or  to  very  soft  shales. 

Two  very  detailed  descriptions  have  appeared  of  work  done 
with  the  earth  auger,  and  as  the  two  accounts  taken  together 
cover  very  fully  the  entire  range  of  exploratory  work  that  can 
be  handled  economically  by  the  use  of  the  auger,  they  will  be 
quoted  almost  in  full. 

The  Auger  in  Light  Work.  —  Mr.  Charles  Catlett  has  made 
extensive  use  of  the  earth  auger  in  testing  brown  ore  deposits 
occurring  interbedded  with  clays  and  sands  at  rather  shallow 
depths.  His  description*  of  outfit  and  results  is  as  follows: 

1.  An  auger  bit  of  steel  or  Swedish  iron,  with  a  steel  point, 
twisted  into  a  spiral,  with  an  ultimate  diameter  of  2  inches,  and 
an  ultimate  thickness  of  blade  of  not  less  than  \  inch.     The 
point  is  found  more  effective  when  split.     The  length  of  the 
auger  proper  was  gradually  increased  until  about  13  inches  was 
reached  as  the  apparent  maximum  which  could  be  used  effec- 
tively.    The  13-inch  auger  contains  four  turns.     This  was  welded 
to  the  end  of  18  inches  of  1-inch  wrought-iron  pipe,  on  which 
screws  were  cut  for  connection. 

2.  One  foot  of  If-inch  octagonal  steel,  with  a  2-inch  cutting 
face,  which  is  likewise  welded  onto  18  inches  of  pipe,  cut  for 
connections. 

3.  Ten  feet  of  IJ-inch  iron  rod,  threaded  at  either  end  for 
connection  with  1-inch  pipe.     When  connected  with  one  of  the 
drill  bits  this  becomes  a  jumper  for  starting  holes  through  hard 
material.     It  is  also  used  when  desired  to  give  additional  weight 
to  the  drill  in  going  through  rock  below  the  surface. 

4.  Sections  of  1-inch  pipe  and  connections. 

5.  An  iron  handle,  with  a  total  length  of  2  feet,  arranged 
with  a  central  eye  for  sliding  up  and  down  the  pipe  and  with 
a  set  screw  for  fastening  it  at  any  point. 

6.  A  sand  pump,  consisting  of  1  or  2  feet  of  1-inch  pipe, 
with  a  simple  leather  valve  and  a  cord  for  raising  and  lowering  it. 

*  Trans.  Am.  Inst.  Mining  Engrs.,  vol.  27,  pp,  127,  128, 


250  BUILDING  STONES  AND  CLAYS 

7.  Two  pairs  of  pipe  tongs  or  two  monkey  wrenches,  with 
attachments  for  turning  them  into  pipe  tongs. 

8.  Sundries:  25  feet  of  tape,  oil  can,  flat  file,  cheap  spring 
balance,  water  bucket,  etc. 

The  auger  is  used  by  two  men,  who,  standing  on  opposite 
sides,  turn  it  by  means  of  the  handle.  The  handle  is  also  useful 
in  giving  a  good  purchase  for  starting  the  auger  from  the  bottom 
of  the  hole,  in  opposition  to  the  air  pressure,  which  is  considerable. 
Enough  water  is  continually  used  to  just  soften  the  material. 
Usually  the  auger  brings  up  a  small  portion,  which  is  dry  and 
unaffected.  Every  few  minutes,  as  the  auger  becomes  full,  it 
is  lifted  out,  scraped  off,  and  replaced.  The  handle  is  moved  up 
and  tightened  by  means  of  the  set  screw  as  the  auger  goes  down. 
At  every  slight  change  of  the  material  the  depth  and  the  character 
of  the  material  are  recorded. 

When  hard  material  is  encountered  the  auger  bit  is  screwed 
off  and  the  drill  bit  screwed  on,  thus  forming  a  churn  drill,  which 
may  be  used  for  passing  through  the  hard  material,  the  auger 
being  replaced  when  softer  material  is  reached.  The  churn  drill 
is  used  by  lifting  it  and  letting  it  fall,  turning  it  slightly  each 
time.  Its  weight  makes  it  cut  quite  rapidly.  When  the  drill  is 
used  the  muck  is  either  worked  stiff  enough  to  admit  of  its  being 
withdrawn  with  the  auger,  or  it  is  extracted  by  means  of  the 
sand  pump  or  a  hickory  swab.  In  either  case  the  material  is 
washed  and  a  sample  is  obtained  of  the  stratum  through  which 
the  drill  is  cutting. 

Of  course  the  best  work  with  such  tools  is  done  on  soft 
material,  but  it  is  entirely  practicable  to  go  through  hard  ma- 
terial (a  few  feet  of  quartzite  or  flint,  and  many  feet  of  ore  being 
often  encountered  in  a  single  hole),  and  the  ability  of  this  simple 
contrivance  to  go  through  interbedded  layers  of  hard  and  soft 
substances  makes  it  very  efficient. 

The  cost  per  foot  increases  considerably  with  depths  exceed- 
ing 50  feet,  but  at  the  greatest  depth  I  attained  (some  80  feet) 
I  did  not  reach  either  its  capacity  or  the  limit  of  its  economical 
use  as  compared  with  other  methods. 

Up  to  25  feet  two  men  can  operate  it;  from  25  feet  to  35  feet 
three  men  are  necessary;  from  that  to  50  feet  a  rough  frame, 
15  feet  to  20  feet  high  (costing  something  over  $1.00),  for  the 
third  man  to  stand  on,  is  required.  The  frame  can  be  moved 
from  point  to  point.  Above  50  feet  it  is  generally  necessary  to 
take  off  one  or  two  of  the  top  joints  each  time  the  auger  or  drill 
is  lifted. 


FIELD  EXAMINATION  OF  CLAY  DEPOSITS 


251 


Feet. 

and  gravel 2 

Yellow  clay 2 

Clay  with  some  ore 4 

Solid  ore 5 

White  clay  and  ore 3 

Total  thickness 16 

Sunk  by  two  men  in  ten  hours. 

B. 

Loose  dirt 3 

Blue  clay 7 

Shale  ore 3 

Wash  ore 9 

Shale  ore 3 

Wash  ore 15 

Total  thickness 40 

Sunk  by  two  men  in  eleven  hours 
plus  three  men  for  four  hours. 

C. 

Yellow  clay 12 

Black  flint f 

Yellow  clay 2| 

White  sand 1 

Solid  sandstone 2 

Total  thickness 18 

Sunk  by  two  men  in  five  hours. 

D. 

Sand  and  gravel 1 

Clay 28 

Total  thickness 29 

Sunk  by  two  men  in  five  hours. 

E. 

Yellow  Clay , 14 

Solid  ore 3 

Clay 1 

Ore 5| 

Clay 2| 

Total  thickness 26 

Sunk  by  two  men  in  six  hours. 


F. 

Feet. 

Sand 1 

Shale  ore 4 

Clay  and  sand 9 

Sandstone 5 

Total  thickness 19 

Sunk  by  two  men  in  8£  hours. 

G. 

Red  clay  and  sandstone 19 

Clay 31 

Clay  and  flint 2 

Total 52 

Two  men  fifteen  hours  plus  three 
men  four  hours. 

H. 

Sand  and  boulders 12 

Clay  and  ore 19 

Clay  and  flint 3 

Clay  and  a  little  ore 19 

Clay  and  much  ore 2 

Clay  and  a  little  ore 5 

Clay 3 

63 

Two  men  for  five  hours  plus  three 
men  for  twenty-five  hours. 


Ft.        Hrs. 


A.. 
B.. 
C.. 
D.. 
E.. 
F.. 
G.. 
H.. 


16 
40 
18 
29 
26 
19 
52 
63 


20 
34 
10 
10 
12 
17 
42 
85 


Ft.  per 
hour. 

0.80 
1.18 
1.80 
2.90 
2.17 
1.12 
1.24 
0.74 


263      230        1.14 


252  BUILDING  STONES  AND   CLAYS 

The  Auger  in  Heavy  Work.  —  The  most  extensive  use  to  which 
the  auger  has  been  put  in  testing  clay  deposits  was  probably  in 
the  course  of  the  examination  of  the  Hudson  River  clay  deposits 
carried  out  some  years  ago  by  Mr.  C.  C.  Jones.  In  this  work 
most  of  the  holes  were  deep  —  40  feet  or  more  —  while  some 
reached  over  100  feet.  This  necessitated  certain  modifications 
both  in  outfit  and  in  the  conduct  of  the  work,  as  is  shown  in 
the  following  description  quoted  from  Mr.  Jones'  paper*  on  the 
subject. 

In  this  work  each  drilling  gang  was  supplied  with  one  20-foot 
hoisting  gin,  one  6-inch  block  and  fall,  100  feet  of  f-inch  rope, 
1  differential  chain  block,  two  1  or  2-inch  augers,  two  handles, 
three  pipe  wrenches,  12  feet  of  IJ-inch  iron  rod,  102  feet  of 
J-inch  and  inch  pipe,  in  6  and  12-feet  sections,  from  20  to  50  feet 
of  1J  or  3-inch  pipe  for  casing,  1  rock  drill,  chains,  etc.  The 
portable  hoisting  gin  was  arranged  to  fold  together  so  as  to  be 
used  as  a  platform  on  which  to  carry  all  the  pipe,  supplies,  etc., 
which  were  lashed  to  it  by  rope.  The  gin,  thus  loaded,  could  be 
carried  by  four  men.  Each  drill  gang  consisted  of  three  men, 
and  the  foreman  of  a  group  of  gangs  aided  when  shifting  position. 

The  holes  varied  in  depth  from  a  few  feet  to  over  100  feet. 
In  all,  about  150  holes  were  sunk,  each  gang  averaging  one  hole 
per  day  for  the  entire  time. 

The  gin  is  made  of  three  pieces  of  good  timber  —  spruce  pref- 
erably —  4  inches  by  4  inches  by  20  feet  in  size.  The  top  of 
each  piece  is  chamfered  and  a  bolt  is  inserted  to  prevent  split- 
ting. The  middle  piece  is,  of  course,  chamfered  on  two  sides, 
and  the  others  on  the  inside  only.  This  is  to  allow  for  the 
spread  of  the  legs  of  the  tripod,  or  gin,  when  it  is  set  up.  On 
the  chamfered  face,  below  the  bolts,  a  hole  is  bored  in  each 
piece  for  a  f-inch  round  iron  bar  to  pass  freely.  The  tops  of 
the  three  timbers,  or  legs  of  the  gin,  are  placed  together;  the 
bar  is  inserted  through  the  hole  in  the  first  leg,  through  one 
eye  of  the  bail,  through  the  hole  in  the  middle  leg,  through  the 
other  eye  of  the  bail,  and  then  through  the  hole  in  the  third 
leg.  One  end  of  the  iron  bar  is  provided  with  a  squared  head, 
and  the  other  with  a  slot,  into  which  a  pin  or  dowel  is  driven, 
after  inserting  the  bar  through  the  third  leg.  The  bail,  of  f- 
inch  round  iron,  thus  hangs  on  the  bar  in  the  spaces  between  the 
legs  of  the  gin.  The  "  drop  "  of  the  bail  should  allow  it  to  pass 
freely  over  the  top  of  the  middle  leg,  i.e.,  the  length  of  the  bail 

*  Trans.  Amer.  Inst.  Mining  Engrs.,  vol.  29,  pp.  40-83. 


FIELD   EXAMINATION  OF  CLAY  DEPOSITS 


253 


•8 

I 


254  BUILDING  STONES  AND   CLAYS 

should  exceed  the  distance  from  the  bar  to  the  top  of  the  timber. 
Sufficient  play  should  be  given  in  all  these  parts  to  have  them 
fit  loosely,  and  washers  should  be  used  to  protect  the  wood. 

Cleats  are  nailed  to  the  middle  leg  of  the  gin  to  form  a  lad- 
der to  the  top  when  erected.  To  erect  the  gin  the  middle  leg- 
is  turned  about  the  bolt  as  a  hinge,  until  it  again  lies  on  the 
ground.  Three  men  grasp  each  a  leg  of  the  gin,  and  by  push- 
ing towards  the  bail  raise  it  in  a  minute.  This  single  maneuver 
suffices  to  erect  the  gin  over  an  exact  point.  To  dismount  it 
the  middle  leg  is  simply  carried  out  until  the  gin  is  lowered  to 
the  ground;  this  leg  is  swung  back  over  the  bolt  again  and  thus 
forms  the  platform  upon  which  everything  is  carried  forward  by 
a  single  trip,  as  above  described,  to  the  next  point  of  operation. 
As  soon  as  the  gin  has  been  erected,  one  man  ascends  the  ladder 
and  hooks  the  wooden  block  over  the  bail,  and  the  fall  is  plumbed 
over  the  exact  point  for  the  bore  hole.  This  is  an  important 
particular,  to  insure  always  a  vertical  stress  in  withdrawing  the 
auger.  The  rope  and  fall  are  now  caught  up  on  one  of  the 
cleats  to  the  side.  The  auger  is  made  from  an  ordinary  wood 
auger  with  2-inch  cutting  face,  which  is  welded  to  a  short  piece 
—  about  18  inches  —  of  black  pipe,  on  one  end  of  which  a  thread 
is  cut.  This  makes  the  bit  about  3  feet  along.  The  handle  is 
about  2  feet  long  over  all,  and  is  made  of  two  pieces  of  f-inch 
round  iron,  welded  to  a  strong  cylindrical  ring,  which  will  pass 
freely  over  couplings  for  1-inch  black  pipe.  The  ring  is  provided 
with  a  strong  |  by  2J-inch  set  screw,  for  securing  the  handle 
to  the  pipe.  The  differential  chain  block  is  Yale  and  Towne's 
J-ton  capacity,  single-chain.  Stillson  pipe  wrenches  are  used, 
two  18-inch  and  one  14-inch,  and  a  small  monkey  wrench  is 
required  for  the  set  screw.  The  section  of  IJ-inch  iron  rod  has 
threads  cut  at  each  end  for  1-inch  pipe  couplings.  The  five  12- 
foot  sections  and  seven  6-foot  sections  of  1-inch  pipe  have  threads 
cut  at  each  end  for  couplings.  Each  section  is  provided  with  a 
coupling  at  one  end,  and  it  is  good  practice  to  have  a  string  of 
extra  couplings  on  hand. 

The  lj-inch  or  3-inch  pipe  for  casing  is  in  4-feet  or  5-feet 
sections,  with  threads  cut  at  each  end  for  couplings.  This  casing 
is  driven  down  when  troublesome  sand  or  gravel  is  encountered 
near  the  surface.  As  a  rule  it  is  little  employed;  but  in  some 
localities  it  is  an  absolute  necessity.  The  drill  is  18  inches  long 
with  a  2-inch  cutting  face,  and:  a  thread  cut  at  the  other  end  for 
1-inch  couplings.  It  is  made  from  IJ-inch  octagon  steel.  The 
chains,  of  f-inch  iron,  with  short  links,  are  3  feet  long,  and  have 
heavy  rings  at  one  end  and  hooks  at  the  other.  An  oil  can  and 
a  small  file,  both  for  couplings,  about  complete  the  outfit  for  each 
boring  gang. 

In  addition  to  this,  a  single  outfit  complete,  exactly  like  the 
foregoing,  but  made  of  J-inch  pipe,  the  auger  and  drill  having 


FIELD  EXAMINATION  OF  CLAY  DEPOSITS  255 

1-inch  cutting  face,  will  be  found  indispensable.  This  can  be 
taken  from  gang  to  gang  as  required.  It  sometimes  happens 
that  a  bore  hole  made  by  the  larger  apparatus  becomes  unex- 
pectedly obstructed  (say,  at  50  to  70  feet)  by  a  pebble,  a  coup- 
ling accidentally  dropped  in,  or  some  other  unfortunate  cause, 
and  all  efforts  at  progress  fail.  This  smaller  apparatus  can  then 
oiten  be  successfully  employed  to  pass  the  obstacle  and  com- 
plete the  test. 

In  commencing  operations,  an  auger  is  attached  to  a  12-foot 
section,  the  handle  is  adjusted,  and  boring  is  begun  at  a  des- 
ignated point,  great  care  being  taken  to  start  vertically,  and  to 
preserve  the  original  orifice.  Neither  more  nor  less  than  five 
turns  of  the  auger  are  required.  This  fills  the  bit,  which  is  then 
drawn  to  the  surface.  One  man  is  always  required  to  attend  to 
the  bit,  as  it  enters  or  emerges  from  the  hole  —  an  insignificant 
but  important  duty.  As  the  hole  deepens  additional  sections 
are  attached,  until  the  assistance  of  the  gin  is  required.  At  this 
period,  after  the  auger  has  received  the  prescribed  number  of 
turns,  the  set  screw  in  the  handle  is  loosened  and  the  handle  is 
allowed  to  drop  to  the  ground.  A  3-foot  chain  is  passed  around 
the  pipe,  the  hook  being  passed  through  the  ring  to  form  a  run- 
ning noose;  the  hook  is  attached  to  the  fall,  and  stress  is  applied. 
After  lifting  the  pipe  to  a  convenient  height  it  is  gripped  at  the 
ground,  either  with  a  wrench  or  by  simply  tilting  one  end  of  the 
handle  so  that  the  ring  binds  against  the  pipe.  The  stress  is 
released  on  the  chain  as  soon  as  the  pipe  is  held  by  the  grip  and 
the  chain  slipped  down  for  a  fresh  hold,  continuing  in  this  manner 
until  the  auger  has  been  completely  extracted.  When  the  depth 
reaches  30  feet,  the  column  of  pipe  must  be  disconnected  at  that 
point.  To  expedite  this  procedure,  a  3-foot  chain  is  looped, 
hook  and  ring,  and  loosely  dropped  around  the  top  of  the  gin. 
As  the  pipe  is  withdrawn  from  the  hole  it  is  so  directed  at  the 
top  as  to  enter  this  loop.  After  withdrawing  the  six  sections  as 
above  described,  the  handle  is  attached  again  below  the  lowest 
coupling  (where  it  already  lies  in  place),  the  30-foot  length  is 
unscrewed,  and  being  held  upright  by  the  loop  at  the  top  of  the 
gin  is  merely  set  at  one  side.  The  chain  on  the  fall  is  again 
attached  to  the  pipe  above  the  handle,  a  stress  applied  to  the 
rope,  the  handle  loosened  as  before,  and  this  process  is  continued 
for  each  30-foot  length  until  the  auger  has  been  withdrawn  from 
any  depth;  the  invariable  rule  being  to  have  always  either  the 
handle  or  the  chain  under  stress  below  a  coupling  attached  to 
the  pipe,  while  the  auger  remains  in  the  hole.  This  operation 
is  reversed  to  lower  the  pipe  again  into  the  hole,  i.e.,  the  sections 
are  replaced  in  the  order  of  their  removal.  It  follows  that  the 
depth  of  the  hole  at  any  time  can  be  ascertained  from  the  number 
of  sections  in  use.  At  depths  exceeding  75  feet  (frequently  less), 
the  chain  block  must  be  used  to  start  the  auger,  hooking  it  on 


256  BUILDING  STONES  AND  CLAYS 

to  the  wooden  fall  when  required.  In  this  manner,  with  a  little 
training  and  a  proper  division  of  the  duties  of  each  man  in  the 
gang,  the  boring  becomes  practically  continuous,  and  proceeds 
very  rapidly.  One  hundred  feet  of  pipe  can  be  started,  pulled 
up,  disconnected,  the  auger  bit  cleaned,  and  the  whole  apparatus 
let  down  into  the  hole  again  in  a  few  minutes. 

When  sand  is  encountered,  enough  water  to  make  it  adhesive 
must  be  poured  into  the  hole,  and  the  auger  will  then  carry  it 
to  the  surface.  Thin  strata  of  sand  cause  difficulty,  and,  simi- 
larly, fine  gravel  is  frequently  impenetrable.  For  holes  of  this 
size  the  various  sand-pump  devices  are  failures,  and  the  auger 
alone  will  do  the  work  better.  The  drill,  with  or  without  the 
iron-rod  section,  offers  the  readiest  solution  to  the  gravel  ques- 
tion. Gravel  must  be  broken  up  6r  pushed  to  one  side.  The 
knack  of  manipulating  the  drill  to  meet  these  circumstances  can 
only  be  imparted  by  experience.  The  best  plan  is  to  instruct 
practically  the  foreman  alone,  who  must  then  deal  personally 
with  the  difficulty  when  it  arises. 

Quicksand  is  another  great  obstacle  to  deep  boring.  If  the 
quantity  of  water  is  small,  and  the  stratum  thin,  it  is  occasionally 
possible  to  penetrate  it  by  very  rapid  work,  and  bore  to  the 
depth  required  for  a  given  purpose;  but  a  thick  seam  is  impene- 
trable by  the  auger,  on  account  of  the  closing  up  of  the  hole 
through  the  vacuum  created  by  withdrawing  the  auger,  or  by 
the  pressure  of  superincumbent  masses.  Casing  will  not  over- 
come this  difficulty.  Ordinarily,  and  especially  in  test  boring 
in  clays,  it  is  unnecessary  to  penetrate  quicksands. 

A  long  chapter  could  not  fully  treat  the  subject  of  accidents. 
A  general  rule  other  than  an  exhortation  to  patience  is  out  of 
the  question,  because  of  the  variety  of  these  seemingly  trifling 
mishaps.  Grappling  devices  to  remove  accidental  obstacles  in 
a  bore  hole  are  all  excellent  in  theory,  but  the  simplest  devices 
often  succeed  where  the  more  elaborate  fail.  A  section  of  pipe 
becoming  disconnected  in  the  bore  hole  can  be  caught  up  by 
using  the  disjointed  member  provided  with  a  clean,  freshly-oiled 
coupling;  a  coupling  can  often  be  removed  from  a  hole  by  using 
a  taper-pointed  stick  driven  into  the  end  of  the  pipe;  an  auger 
broken  at  the  shank  may  be  grasped  by  a  noose  of  short-link 
chain  lowered  by  two  strings,  which  is  then  grappled  by  a  hook 
on  the  end  of  the  i-inch  rod  or  pipe,  or  entangled  around  the 
small  drill.  Most  of  the  mishaps  happen  through  neglect  of  the 
simple  rules  given.  It  is  important  always  to  avoid  gorging 
the  auger  at  great  depths.  It  is  apt  to  be  frequently  clogged  at 
the  bottom  of  a  long  column  of  pipe,  and  it  is  not  advisable  to 
then  reverse  the  auger  to  release  it. 


FIELD  EXAMINATION  OF  CLAY  DEPOSITS  257 

References  on  Methods  of  Field  Examination.  — 

Bleininger,   A.   V.    The  manufacture  of  hydraulic  cements.     Bull.   4, 

Ohio  Geol.  Survey,  1904.     See  pp.  102-108. 
Catlett,  C.     The  hand-auger  and  hand-drill  in  prospecting  work.     Trans. 

Amer.  Inst.  Mining  Engrs.,  Vol.  27,  pp.  123-129.     1898. 
Darton,  N.  H.     On  a  jointed  earth-auger  for  geological  exploration  in 

soft  deposits.     American  Geologist,  Vol.  7,  p.  117.     1891. 
Jones,  C.  C.     A  geologic  and  economic  survey  of  the  clay  deposits  of  the 

lower  Hudson  River  Valley.     Trans.  Amer.  Inst.  Mining  Engrs., 

Vol.  29,  pp.  40-83.     1900. 

Determination  of  Composition  and  Tonnage. 

Errors  in  Sampling.  —  In  sampling  clays  from  a  natural  out- 
crop, or  even  from  an  artificial  cut  which  has  stood  for  any 
length  of  time,  it  must  be  borne  in  mind  that  there  are  two  dis- 
tinct opportunities  for  serious  error. 

The  first  is  due  to  purely  physical  causes,  and  arises  from  the 
very  yielding  nature  of  clays  when  exposed  for  a  time  to  atmos- 
pheric action.  Parts  of  the  face  of  the  outcrop  or  cut  rare  likely 
to  have  slipped  down  considerably,  so  that  the  exposure  does 
not  represent  the  true  character  of  the  clay. 

The  second  chance  for  error  arises  from  the  fact  that,  when 
clays  or  shales  are  exposed  to  the  action  of  rain  or  surface  waters 
for  any  length  of  time,  the  surface  clay  will  be  robbed  of  its  more 
soluble  or  changeable  constituents.  The  outcrop  is,  therefore, 
likely  to  show  lower  percentages  of  lime,  magnesia,  alkalies  and 
sulphur  than  the  same  clay  body  carries  in  depth.  A  sample 
taken  from  the  outcrop  might,  on  analysis,  show  a  refractory 
clay  practically  free  from  these  fluxing  constituents,  while  ten 
or  fifteen  feet  below  the  outcrop  the  fresh  clay  might  contain  so 
much  lime,  alkalies,  etc.,  as  to  be  of  very  inferior  grade.  The 
analyses  quoted  below  illustrate  very  clearly  the  differences  which 
may  be  expected  to  occur  between  fresh  unweathered  clay  and 
the  clay  as  it  outcrops.  Both  the  analyses  quoted  are  of  clays 
from  Croton  Point,  New  York. 

It  will  be  seen  that  the  blue  unweathered  clay  (A)  contains 
more  than  twice  as  much  lime  as  the  yellow  weathered  clay  (B). 
Weathering  has  also  slightly  reduced  the  magnesia,  and  has 
affected  the  alkalies  very  markedly.  The  insoluble  constituents 
—  silica,  alumina  and  iron  —  are  in  consequence  of  this  leaching 
relatively  increased  in  the  weathered  clay. 


258 


BUILDING  STONES  AND  CLAYS 


A. 

B. 

Silica  (SiO«). 

51  61 

56  75 

Alumina  (A^Oj 

19  20 

20  15 

Iron  oxide  (Fea 

O3)  

8  19 

8  82 

Lime  (CaO) 

7  60 

3  14 

Magnesia  (Mg( 

)) 

1  25 

1  20 

Alkalies  (K2O, 

Na2O)  .  .  . 

5  32 

4  50 

Carbon  dioxide 

(CO,)  I 

Sen 

Water  

\ 

7.25 

.4MB 

Estimation  of  Tonnage.  —  On  ihe  pages  immediately  follow- 
ing several  long  series  of  tests  of  the  specific  gravity  and  weights 
of  a  large  number  of  clays  and  shales  are  quoted  and  discussed. 
From  the  data  there  given  the  following  rules  can  be  considered 


(1)  Ordinary  soft  clays  will  average  120  pounds  per  cubic 
foot,  or  3240  pounds  per  cubic  yard,  in  the  bank. 

(2)  Shales  will  average  150  pounds  per  cubic  foot,  or  4050 
pounds  per  cubic  yard. 

For  rough  calculations  as  to  tonnage,  it  may,  therefore,  be 
assumed  that  clays  will  weigh  If  tons,  and  shales  2  tons,  per  cubic 
yard. 

Prof.  G.  H.  Cook,  in  1874,  determined*  the  specific  gravity  of 
a  large  series  of  clays  from  New  Jersey.  In  making  this  deter- 
mination "  a  prism  about  an  inch  in  length  was  cut  out  of  the 
solid  mass.  This  was  covered  by  a  film  of  paraffin  and  weighed, 
first  in  air,  then  in  water."  The  values  thus  obtained  are,  there- 
fore, close  approximations  to  the  density  of  the  clay  as  it  occurs 
in  nature,  and  when  multiplied  by  62.4  will  give  the  weight  per 
cubic  foot  of  the  product  in  the  bank.  The  values  varied  from 
1.539  to  2.170,  the  average  of  the  86  samples  of  unwashed  clays 
being  1.824.  Converted  into  pounds  per  cubic  foot,  these  values 
are  as  follows: 


Specific  grav- 
ity. 

Pounds  per 
cubic  foot. 

IMaximum 

2  170 

135  41 

Average 

1.824 

113.82 

Minimum                                                    .... 

1.539 

96.03 

*  Report  on  the  Clay  Deposits  of  New  Jersey,  1878,  pp.  283-286. 


FIELD  EXAMINATION  OF  CLAY  DEPOSITS 


259 


Part  of  this  great  variation  in  density  was  due  to  the  variations 
in  furnaces,  etc.,  but  much  of  it  was  directly  traceable  to  the 
varying  percentages  of  sand  contained  in  the  clays.  The  table 
following  illustrates  this  point. 

TABLE  113.  —  RELATION   BETWEEN   SPECIFIC   GRAVITY   AND 
SAND  PERCENTAGES.     (CooK.) 


Specific  gravity. 

Per  cent  of  sand. 

Specific  gravity. 

Per  cent  of  sand. 

2.321 

58.40 

1.607-1.612 

8.60 

2.283 

57.10 

1.743-1.789 

6.51 

2.052-2.101 

56.80 

1.657-1.705 

3.10 

2.047-2.077 

48.40 

1.764-1.769 

1.10 

1.981-2.023 

40.50 

1.766-1.893 

0.80 

1.971-2.138 

39.95 

1.528-1.542 

0.71 

2.012-2.022 

37.85 

1.738 

0.70 

2.129-2.151 

37.10 

1.731-1.809 

0.50 

1.994-2.047 

28.81 

1.578-1.610 

0.50 

1.705-1.732 

27.80 

1.723-1.742 

0.20 

1.861-1.864 

20.60 

In  1896  Wheeler  reported  the  specific  gravities  of  a  series  of 
153  Missouri  clays,  of  several  widely  different  types.  His  re- 
sults, grouped  by  classes,  are  given  in  the  following  table. 

TABLE  114.  —  SPECIFIC  GRAVITY  OF  MISSOURI  CLAYS.  (WHEELER.) 


i  ype  01  ciay. 

Minimum. 

Average. 

Maximum. 

Kaolins  (residual)          

1.69 

1.90 

2.02 

Loess  clays 

1  69 

2  05 

2  17 

Gumbo  clays 

1  98 

2  01 

2  05 

Tertiary  clays 

1  93 

2  03 

2  13 

Fire  clays  (shales) 

2  23 

2  40 

2  54 

Nonrefractory  shales. 

2  15 

2  38 

2  56 

Specific  gravity. 


In  recent  clay  investigations*  carried  on  by  the  New  Jersey 
Geological  Survey  a  series  of  31  clay  samples  were  tested  for 
specific  gravity.  In  this  case  the  clays  were  powdered,  and  the 
specific  gravity  was  then  determined  by  the  use  of  the  pycnom- 
eter.  Since  this  method  disregards  the  air  spaces  in  the  clay, 
and  really  gives  the  specific  gravity  of  the  mineral  particles,  the 
results,  as  might  have  been  expected,  gave  much  larger  values  than 

*  Vol.  VI,  Reports  New  Jersey  Geol.  Survey,  p.  115,  1904. 


260 


BUILDING  STONES  AND   CLAYS 


those  reported  by  Cook.  The  minimum  specific  gravity  found 
was  2.39;  the  highest,  2.84;  while  the  average  for  the  31  samples 
was  2.584. 

A  similar  series  of  32  Iowa  clays  gave*  a  minimum  value  of 
2.25;  a  maximum,  2.64;  and  average,  2.46. 

For  the  purposes  of  the  engineer  or  manufacturer,  these  Iowa 
and  the  later  New  Jersey  attempts  to  determine  the  "  true 
specific  gravity  "  of  clays  may  be  disregarded  entirely;  for  the 
values  found  by  this  method  are  not  of  the  slightest  economic 
importance.  Neither  engineer  nor  manufacturer  has  any  interest 
in  knowing  the  "  true  specific  gravity  "  of  a  clay  in  a  state  of 
theoretically  maximum  density,  free  from  all  air  spaces;  for 
such  clays  do  not  occur  in  nature.  What  we  do  want  to  know 
is  the  weight  per  cubic  foot  of  clay  as  it  occurs  in  the  clay  bank, 
and  fortunately  the  older  work  of  Cook  and  Wheeler  gives  the 
desired  information. 

The  two  sets  of  results  (Cook  and  Wheeler),  when  combined 
and  divided  merely  into  the  two  natural  groups  of  (1)  ordinary 
clays  and  (2)  hard  shales,  give  the  following  results: 

TABLE   115.  — SPECIFIC  GRAVITY  AND  WEIGHT  OF  CLAYS. 


Kind. 

Specific  gravity. 

Weight  in  pounds  per 
cubic  foot. 

Mini- 
mum. 

Aver- 
age. 

Maxi- 
mum. 

Mini- 
mum. 

Aver- 
age. 

Maxi- 
mum. 

Clay 

1.539 
2.15 

1.90 

2.39 

2.17 
2.56 

96 
134.2 

118.6 
149.1 

135.4 
161.7 

Shale                   

These  figures  may,  therefore,  be  used  in  calculations.  For 
convenience  it  may  be  considered,  without  sensible  error,  that  a 
cubic  foot  of  clay,  in  the  bank,  will  average  120  pounds,  while 
a  cubic  foot  of  shale  will  average  150  pounds. 


Vol.  XIV,  Reports  Iowa  Geol.  Survey,  p.  116. 


INDEX 


Abrasion  tests,  216. 

Absorption  tests,  198-202,  203. 

Acid  rocks,  9,  23. 

Acid  tests,  207-210. 

Albite,  25. 

Amphibole,  27,  34. 

Analyses: 

average  igneous  rocks,  8,  23. 
granite,  43. 
limestone,  8,  154. 
sandstone,  8,  128. 
shale,  8,  98. 
slate,  8,  97. 

basic  rocks,  224. 

feldspars,  26. 

granites,  43-55. 

hornblende,  28. 

kaolinite,  222. 

limestone  clays,  230. 

limestones,  155-156. 

loess  clays,  236. 

marbles,  169-171,  178. 

marine  clays,  232. 

micas,  27. 

pholerite,  222. 

residual  clays,  223,  224,  227. 

sandstones,  131-136. 

serpentine,  83-84. 

shale  clays,  225. 

shells,  151. 

slates,  8,  97,  99,  100,  103-108. 

stream  clays,  234. 

trap,  72-76. 
Anorthite,  25. 
Anticline,  13. 
Ash  slates,  99-100. 
Ash,  volcanic,  20-21,  128. 
Auger,  earth,  249-257. 
Augite,  27,  34. 


Basalt,  30,  70. 

Basic  rocks,  9,  23,  70-80,  81-90,  224. 

Batholith,  19. 

Bedding,  93. 

Bibliographies  (see  reference  list). 

Biotite,  26,  34. 

Bluestone,  144,  146. 

Bond  issues,  190-193. 

Bosses,  igneous,  19. 

Brard  test,  205-207. 

Breccia,  137. 


Calcareous  tufa,  157. 

Calcite,  154. 

Cementing  materials  of  sandstones, 

137. 

Chalk,  157. 

Chemical  composition  (see  analyses). 
Chemical  relation  of  rock,  7. 
Chert,  153,  157. 
Chlorite,  28. 

Cleavage  of  slates,  110-111. 
Coastal  Plain  clays,  238-240. 
Color  of  granites,  35. 

limestones,  156. 

marbles,  177. 

slates,  108-110. 

stone,  186. 

trap,  79. 

Composition,  chemical  (see  analyses). 
Compressive  strength,  214-215. 

granites,  55-60. 

limestones,  158-159. 

marbles,  172-173. 

sandstones,  139-142. 

serpentines,  85-86. 

traps,  77. 
Cone,  volcanic,  20. 


261 


262 


INDEX 


Conglomerate,  137. 

Costs,  stone  industry,  190-191. 

Density  (see  specific  gravity). 

Diabase,  70. 

Diamond-drill  work,  183-184. 

Dike,  20. 

Diorite,  29,  70,  224. 

Dip,  11. 

Dolomite,  152. 

Dressing  of  slate,  115-119. 

Earth  history,  1. 
Earth  auger,  249-257. 
Elseolite,  34. 
Elevation  of  land,  2. 
Engineering  geology,  1. 
Examination  of  clay  properties,  244- 

260. 
Examination  of  stone  properties,  182- 

194. 
Expansion  of  stone,  202. 

Faults,  13. 

Feldspar,  25,  34. 

Feldspar,  decay  of,  221-223. 

Felsite,  30. 

Financing  stone  industry,  189-194. 

Fire  resistance,  210-217. 

Flagstones,  143. 

Flint,  153. 

Folds  in  rock,  12. 

Frost  tests,  203-207. 

Gabbro,  29,  70. 

Geologic  ages,  3,  4. 

Geologic  chronology,  3. 

Glacial  clays,  234. 

Glacial  limit,  238. 

Glacial  period,  2. 

Glass,  volcanic,  21,  30. 

Gneiss,  22,  30,  37. 

Grain  (in  granite),  15,  39. 

Grains,  size  of,  37,  137,  185. 

Granite,  29-69. 

Gravel,  10,  127. 

Gravity  (see  specific  gravity). 

Graywacke,  143. 


Hardness  of  stone,  216. 
Heat  resistance,  210-214. 
Hornblende,  27,  82. 
Hornblendite,  29,  70. 

Ice-borne  clays,  234. 
Igneous  action,  17. 
Igneous  rocks,  5,  17-90. 
Igneous  slates,  99-101. 
Impact  tests,  112. 
Intrusives,  17. 
"Isinglass,"  26. 

Joints,  14,  186. 
Kaolinite,  222. 

Laboratory  tests  of  stone,  195-217. 

Labradorite,  25. 

Laccolith,  19. 

Lake  clays,  234. 

Laminated  igneous  rocks,  22,  37. 

Lava,  20,  31. 

Limestones,  150-165,  227-230. 

Loess  clays,  234,  236. 

Magnesia  and  limestones,  152. 

Marbles,  157,  166-181. 

Marine  clays,  231-232. 

Marl,  157. 

Mass  of  igneous  rocks,  22. 

Metamorphic  rocks,  6,  11,  93,  95-96, 

113. 

Mica,  26,  34. 
Microcline,  25. 
Mille  (of  slate),  120. 
Minerals  in  granite,  34,  36. 
Minerals  in  trap,  71. 
Minerals,  rock-forming,  25. 
Monocline,  12. 
Muscovite,  26,  34. 

Neck,  volcanic,  20. 
Nepheline,  34. 
Norite. 

Oligoclase,  25. 
Olivine,  28,  82. 


INDEX 


263 


Onyx  marbles,  166,  180-181. 
Oolitic  limestones,  157. 
Ophicalcite,  82,  84. 
Ophimagnesite,  82,  84. 
Origin  of  clays,  218-237. 
Origin  of  rock,  8-11. 
Orthoclase,  25. 
Output  (see  production  statistics). 

Paving  blocks,  65,  78,  79. 
Pegmatites,  37. 
Peridot,  28. 
Peridotite,  30,  70. 
Pholerite,  222. 
Plagioclase,  25. 
Porosity,  198-202. 
Porphyry,  30. 
Pozzuolana,  31. 
Production,  statistics  of: 

granite,  61-67. 

limestone,  162-165. 

marble,  174-175,  179-180. 

sandstone,  144-147. 

slate,  122-125. 

soapstone  and  talc,  88-90. 
Profits  of  stone  industry,  190-191. 
Pumice,  21,  31. 
Puzzolan  materials,  31. 
Pyrite  in  limestone,  153. 
Pyrite  in  serpentine,  85. 
Pyroxene,  27,  82. 
Pyroxenite,  29,  70,  224. 

Quarry  examination,  182-184. 
Quarry  finances,  190-191. 
Quartz,  25-34. 
Quartzite,  142. 

Reference  lists: 

building  stone,  testing,  216-217. 
clays,  distribution,  240-243. 
clays,  examination,  257. 
clays,  origin,  236-237. 
granites,  68-69. 
limestone,  160-162. 
marbles,  crystalline,  175-177. 
marbles,  subcrystalline,  180. 


Reference  lists  (continued): 

marbles,  onyx,  181. 

sandstones,  148-149. 

serpentine,  87. 

slate,  distribution,  125-126. 

slate,  origin,  102. 

slate,  testing,  113. 

soapstone  and  talc,  90. 

trap,  80. 

Residual  clays,  219,  221-230. 
Rift  (in  granite),  15,  39. 

Sand,  10,  127. 

Sandstone,  127-149,  227. 

Sedimentary  rocks,  6,  91. 

Serpentine,  31,  81-87. 

Shale  clays,  224-227,  232-233. 

Sheets  (igneous),  19,  20. 

Sheet  structure  (in  granites),  39. 

Shells,  composition  of,  151. 

Sills  (igneous),  20. 

Sizes  of  slate,  120-121. 

Slate,  95-126. 

Soapstone,  87-90. 

Sodium-sulphate  test,  205-207. 

Specific  gravity,  198-202. 

acid  rocks,  55-60. 

basic  rocks,  75,  85,  86. 

clays,  258-260. 

granites,  55-60. 

limestone,  157,  159. 

marbles,  172-173. 

sandstones,  139-142. 

serpentine,  85,  86. 

shale,  258-260. 

slate,  112. 

trap,  77. 

Square  (of  slate),  119. 
Statistics  (see  production  statistics). 
Stocks  (igneous),  19. 
Stock  issues,  194-195. 
Stream  clays,  233-234. 
Strength  (see  compressive  strength). 
Strength  (see  transverse  strength). 
Strike  of  rocks,  11. 
Sulphate  of  soda  test,  205-207. 
Syenite,  29,  34. 
Syncline,  12. 


264 


INDEX 


Talc,  81,  87-90. 
Terraces,  river,  233-234. 
Testing  methods,  stone,  195-217. 
Thickness  of  slates,  121. 
Transported  clays,  231-237. 
Transverse  strength,  216. 

granites,  60. 

slates,  112. 
Trap,  30,  31,  70-80. 
Travertine,  157. 
Tufa,  calcareous,  157. 
Tuff,  128. 

Verde  antique,  81-87. 
Volcanic  ash,  20,  21,  128. 


Volcanic  products,  19,  21. 
Volcanoes,  19. 

Wear,  resistance  to,  216. 
Weathering,  188,  221-230,  257-258. 
Weight  per  cubic  foot,  198-202. 

clays,  258-260. 

granites,  55,  60. 

limestones,  157,  159. 

marbles,  172,  173. 

sandstones,  139-142. 

serpentines,  85,  86. 

shales,  258-260 

trap,  77. 
Wind-borne  clays,  234,  236. 


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Black's  United  States  Public  Works Oblong  4to,  5  00 

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